drm/amdgpu: fix the page fault caused by uninitialized variables

This patch will fix the page fault caused by uninitialized variables.

Error Log:
......
[ 130.246323] [drm] GART: num cpu pages 131072, num gpu pages 131072
[ 131.963112] [drm] PCIE GART of 512M enabled (table at 0x0000008000000000).
[ 131.963130] BUG: unable to handle page fault for address: 000000000002db80
[ 131.963181] #PF: supervisor write access in kernel mode
[ 131.963210] #PF: error_code(0x0002) - not-present page
[ 131.963233] PGD 0 P4D 0
[ 131.963253] Oops: 0002 [#1] SMP NOPTI
[ 131.963273] CPU: 3 PID: 1411 Comm: modprobe Not tainted 5.13.0+ #1
[ 131.963338] RIP: 0010:osq_lock+0x4d/0x120
[ 131.963381] Code: 10 00 00 00 00 48 c7 02 00 00 00 00 89 42 14 87 07 85 c0 0f 84 d0 00 00 00 83 e8 01 48 98 48 03 0c c5 00 d9 ea 9c 48 89 4a 08 <48> 89 11 44 8b 42 10 45 85 c0 0f 85 af 00 00 00 55 48 89 fe 65 4c
[ 131.963460] RSP: 0018:ffffa40481717768 EFLAGS: 00010202
[ 131.963483] RAX: fffffffffffffffe RBX: ffffa40481717920 RCX: 000000000002db80
[ 131.963520] RDX: ffff9256fecedb80 RSI: ffff9256cbed2e80 RDI: ffffa40481717ac4
[ 131.963547] RBP: ffffa40481717808 R08: ffffa40481717920 R09: 00000000ffffffff
[ 131.963582] R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000000
[ 131.963609] R13: ffffa40481717ac4 R14: ffffa40481717ab8 R15: ffff9256c9480000
[ 131.963646] FS: 00007f23d9b9c540(0000) GS:ffff9256fecc0000(0000) knlGS:0000000000000000
[ 131.963687] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 131.963721] CR2: 000000000002db80 CR3: 0000000008444000 CR4: 00000000000506e0
[ 131.963758] Call Trace:
[ 131.963772] ? __ww_mutex_lock.isra.0+0x3a2/0x760
[ 131.963810] ? prb_read_valid+0x1c/0x20
[ 131.963830] ? console_unlock+0x2fe/0x4f0
[ 131.963849] __ww_mutex_lock_interruptible_slowpath+0x16/0x20
[ 131.963882] ww_mutex_lock_interruptible+0x83/0x90
[ 131.963908] amdgpu_bo_create_reserved+0xf0/0x1e0 [amdgpu]
[ 131.964237] amdgpu_bo_create_kernel+0x17/0x80 [amdgpu]
[ 131.964509] amdgpu_gmc_vram_checking+0x41/0xf0 [amdgpu]
[ 131.964807] gmc_v10_0_hw_init+0x105/0x120 [amdgpu]
[ 131.965108] amdgpu_device_init.cold+0x1aa4/0x1e3e [amdgpu]
......
Signed-off-by: Xiaojian Du <Xiaojian.Du@amd.com>
Reviewed-by: Yang Wang <kevinyang.wang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -825,9 +825,9 @@ void amdgpu_gmc_get_reserved_allocation(struct amdgpu_device *adev)
 
 int amdgpu_gmc_vram_checking(struct amdgpu_device *adev)
 {
-	struct amdgpu_bo *vram_bo;
-	uint64_t vram_gpu;
-	void *vram_ptr;
+	struct amdgpu_bo *vram_bo = NULL;
+	uint64_t vram_gpu = 0;
+	void *vram_ptr = NULL;
 
 	int ret, size = 0x100000;
 	uint8_t cptr[10];