media: vim2m: replace devm_kzalloc by kzalloc

It is not possible to use devm_kzalloc since that memory is
freed immediately when the device instance is unbound.

Various objects like the video device may still be in use
since someone has the device node open, and when that is closed
it expects the memory to be around.

So use kzalloc and release it at the appropriate time.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>