media: coda: jpeg: add NULL check after kmalloc

Fixes coccicheck warning:

./drivers/media/platform/coda/coda-jpeg.c:331:3-31:
	alloc with no test, possible model on line 354

Add NULL check after kmalloc.

Signed-off-by: Chen Zhou <chenzhou10@huawei.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>