drm/amdgpu: release drm_device after amdgpu_driver_unload_kms

If we release drm_device before amdgpu_driver_unload_kms,
then it will raise the error below. Therefore, we need to
place it before amdgpu_driver_unload_kms.
[   43.055736] Memory manager not clean during takedown.
[   43.055777] WARNING: CPU: 1 PID: 2807 at /build/linux-hwe-9KJ07q/linux-hwe-4.18.0/drivers/gpu/drm/drm_mm.c:913 drm_mm_takedown+0x24/0x30 [drm]
[   43.055778] Modules linked in: amdgpu(OE-) amd_sched(OE) amdttm(OE) amdkcl(OE) amd_iommu_v2 drm_kms_helper drm i2c_algo_bit fb_sys_fops syscopyarea sysfillrect sysimgblt snd_hda_codec_generic nfit kvm_intel kvm irqbypass crct10dif_pclmul crc32_pclmul snd_hda_intel snd_hda_codec snd_hda_core snd_hwdep snd_pcm ghash_clmulni_intel snd_seq_midi snd_seq_midi_event pcbc snd_rawmidi snd_seq snd_seq_device aesni_intel snd_timer joydev aes_x86_64 crypto_simd cryptd glue_helper snd soundcore input_leds mac_hid serio_raw qemu_fw_cfg binfmt_misc sch_fq_codel nfsd auth_rpcgss nfs_acl lockd grace sunrpc parport_pc ppdev lp parport ip_tables x_tables autofs4 hid_generic floppy usbhid psmouse hid i2c_piix4 e1000 pata_acpi
[   43.055819] CPU: 1 PID: 2807 Comm: modprobe Tainted: G           OE     4.18.0-15-generic #16~18.04.1-Ubuntu
[   43.055820] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
[   43.055830] RIP: 0010:drm_mm_takedown+0x24/0x30 [drm]
[   43.055831] Code: 84 00 00 00 00 00 0f 1f 44 00 00 48 8b 47 38 48 83 c7 38 48 39 c7 75 02 f3 c3 55 48 c7 c7 38 33 80 c0 48 89 e5 e8 1c 41 ec d0 <0f> 0b 5d c3 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48 89 e5 41
[   43.055857] RSP: 0018:ffffae33c1393d28 EFLAGS: 00010286
[   43.055859] RAX: 0000000000000000 RBX: ffff9651b4a29800 RCX: 0000000000000006
[   43.055860] RDX: 0000000000000007 RSI: 0000000000000096 RDI: ffff9651bfc964b0
[   43.055861] RBP: ffffae33c1393d28 R08: 00000000000002a6 R09: 0000000000000004
[   43.055861] R10: ffffae33c1393d20 R11: 0000000000000001 R12: ffff9651ba6cb000
[   43.055863] R13: ffff9651b7f40000 R14: ffffffffc0de3a10 R15: ffff9651ba5c6460
[   43.055864] FS:  00007f1d3c08d540(0000) GS:ffff9651bfc80000(0000) knlGS:0000000000000000
[   43.055865] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   43.055866] CR2: 00005630a5831640 CR3: 000000012e274004 CR4: 00000000003606e0
[   43.055870] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   43.055871] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   43.055871] Call Trace:
[   43.055885]  drm_vma_offset_manager_destroy+0x1b/0x30 [drm]
[   43.055894]  drm_gem_destroy+0x19/0x40 [drm]
[   43.055903]  drm_dev_fini+0x7f/0x90 [drm]
[   43.055911]  drm_dev_release+0x2b/0x40 [drm]
[   43.055919]  drm_dev_unplug+0x64/0x80 [drm]
[   43.055994]  amdgpu_pci_remove+0x39/0x70 [amdgpu]
[   43.055998]  pci_device_remove+0x3e/0xc0
[   43.056001]  device_release_driver_internal+0x18a/0x260
[   43.056003]  driver_detach+0x3f/0x80
[   43.056004]  bus_remove_driver+0x59/0xd0
[   43.056006]  driver_unregister+0x2c/0x40
[   43.056008]  pci_unregister_driver+0x22/0xa0
[   43.056087]  amdgpu_exit+0x15/0x57c [amdgpu]
[   43.056090]  __x64_sys_delete_module+0x146/0x280
[   43.056094]  do_syscall_64+0x5a/0x120

v2: put drm_dev_put after pci_set_drvdata
Signed-off-by: Yintian Tao <yttao@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c

@@ -1127,10 +1127,10 @@ amdgpu_pci_remove(struct pci_dev *pdev)
 #endif
 		DRM_ERROR("Hotplug removal is not supported\n");
 	drm_dev_unplug(dev);
-	drm_dev_put(dev);
 	amdgpu_driver_unload_kms(dev);
 	pci_disable_device(pdev);
 	pci_set_drvdata(pdev, NULL);
+	drm_dev_put(dev);
 }
 
 static void