LF-3334-05: media: isi: m2m: fix v4l2-compliance G_FMT test fail issue

LF-3334-05: media: isi: m2m: fix v4l2-compliance G_FMT test fail issue

Fix v4l2-compliance G_FMT test fail issue, error log as bellow:
[  110.057121] Unable to handle kernel NULL pointer dereference at virtual address 000000000000000c
  ...
[  110.227985] Call trace:
[  110.230431]  mxc_isi_m2m_g_fmt_vid_cap+0x48/0xb0
[  110.235046]  v4l_g_fmt+0xc8/0x2f0
[  110.238358]  __video_do_ioctl+0x180/0x3e4
[  110.242365]  video_usercopy+0x190/0x410
[  110.246197]  video_ioctl2+0x18/0x24
[  110.249684]  v4l2_ioctl+0x44/0x64
[  110.252998]  __arm64_sys_ioctl+0xa8/0xf0
[  110.256920]  el0_svc_common.constprop.0+0x78/0x1a0
[  110.261708]  do_el0_svc+0x24/0x90
[  110.265022]  el0_svc+0x14/0x20
[  110.268074]  el0_sync_handler+0x1a4/0x1b0
[  110.272080]  el0_sync+0x174/0x180
[  110.275395] Code: b9489405 b9000e65 b9001664 f9446404 (b9400c84)
[  110.281487] ---[ end trace 115fd9c0a779b4d9 ]---

Signed-off-by: Guoniu.zhou <guoniu.zhou@nxp.com>
Reviewed-by: Robby Cai <robby.cai@nxp.com>