media: atomisp2: Remove null check before kfree

Kfree on NULL pointer is a no-op and therefore checking is redundant.

Signed-off-by: Himanshu Jha <himanshujha199640@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>