Fixes this warning:

[  956.730136] ------------[ cut here ]------------
[  956.730143] WARNING: CPU: 1 PID: 10134 at lib/dma-debug.c:963 dma_debug_device_change+0x191/0x1f0()
[  956.730146] pci 0000:07:05.0: DMA-API: device driver has pending DMA allocations while released from device [count=8]
One of leaked entries details: [device address=0x00000000d3d57000] [size=512 bytes] [mapped with DMA_BIDIRECTIONAL] [mapped as coherent]
[  956.730147] Modules linked in: solo6x10(-) videobuf2_dma_contig videobuf2_dma_sg videobuf2_memops videobuf2_core ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat videobuf_vmalloc videobuf_core v4l2_common videodev rt2800usb rt2800lib rt2x00usb rt2x00lib mac80211 cfg80211 crc_ccitt usbkbd hid_a4tech hid_generic usbhid snd_hda_codec_hdmi snd_hda_codec_via snd_hda_codec_generic snd_hda_intel snd_hda_controller snd_hda_codec snd_hwdep snd_pcm x86_pkg_temp_thermal snd_timer snd soundcore
[  956.730172] CPU: 1 PID: 10134 Comm: rmmod Not tainted 3.18.0-rc1-next-20141023-zver-dirty #24
[  956.730173] Hardware name: System manufacturer System Product Name/P8H77-V, BIOS 0501 02/28/2012
[  956.730175]  0000000000000009 ffff8801df9e3c58 ffffffff817ffe6b 0000000000000001
[  956.730177]  ffff8801df9e3ca8 ffff8801df9e3c98 ffffffff81091ec7 0000000000000046
[  956.730180]  ffff880215457e90 0000000000000008 ffffffff81cbb10f ffff880215570098
[  956.730183] Call Trace:
[  956.730188]  [<ffffffff817ffe6b>] dump_stack+0x4f/0x7c
[  956.730192]  [<ffffffff81091ec7>] warn_slowpath_common+0x87/0xb0
[  956.730194]  [<ffffffff81091f91>] warn_slowpath_fmt+0x41/0x50
[  956.730197]  [<ffffffff81412558>] ? dma_debug_device_change+0xb8/0x1f0
[  956.730199]  [<ffffffff81412631>] dma_debug_device_change+0x191/0x1f0
[  956.730203]  [<ffffffff810b14ad>] notifier_call_chain+0x4d/0x70
[  956.730205]  [<ffffffff810b15f9>] __blocking_notifier_call_chain+0x59/0x80
[  956.730207]  [<ffffffff810b1631>] blocking_notifier_call_chain+0x11/0x20
[  956.730211]  [<ffffffff815873af>] __device_release_driver+0xcf/0xf0
[  956.730213]  [<ffffffff81587ee8>] driver_detach+0xc8/0xd0
[  956.730215]  [<ffffffff81587147>] bus_remove_driver+0x57/0xd0
[  956.730218]  [<ffffffff815887e9>] driver_unregister+0x29/0x60
[  956.730221]  [<ffffffff81420131>] pci_unregister_driver+0x21/0x90
[  956.730225]  [<ffffffffa03219d7>] solo_pci_driver_exit+0x10/0x12 [solo6x10]
[  956.730228]  [<ffffffff81112ee0>] SyS_delete_module+0x170/0x1f0
[  956.730232]  [<ffffffff813eb76e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
[  956.730234]  [<ffffffff8180abd2>] system_call_fastpath+0x12/0x17
[  956.730235] ---[ end trace e730af02713a6c53 ]---
[  956.730237] Mapped at:
[  956.730238]  [<ffffffff8141186c>] debug_dma_alloc_coherent+0x3c/0xb0
[  956.730240]  [<ffffffffa03203f6>] solo_enc_v4l2_init+0x706/0xba0 [solo6x10]
[  956.730243]  [<ffffffffa03165b3>] solo_pci_probe+0x503/0x700 [solo6x10]
[  956.730245]  [<ffffffff81420459>] local_pci_probe+0x49/0xa0
[  956.730248]  [<ffffffff814207a1>] pci_device_probe+0xd1/0x120
Signed-off-by: Andrey Utkin <andrey.krieger.utkin@gmail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>