media: atomisp: remove redundant NULL check

Fix below warnings reported by coccicheck:
./drivers/staging/media/atomisp/pci/atomisp_cmd.c:4269:2-8: WARNING:
NULL check before some freeing functions is not needed.
./drivers/staging/media/atomisp/pci/atomisp_cmd.c:4626:2-8: WARNING:
NULL check before some freeing functions is not needed.

Link: https://lore.kernel.org/linux-media/1611220312-89384-3-git-send-email-abaci-bugfix@linux.alibaba.com


Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <abaci-bugfix@linux.alibaba.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>