media: mx2_emmaprp: use struct v4l2_fh

Convert this driver to use struct v4l2_fh and as a result switch to
using vb2/v4l2_mem2mem helper functions as well.

Only compile-tested due to lack of hardware. This driver is however
very similar to the m2m-deinterlace driver in this respect, and that
v4l2_fh conversion has been properly tested.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reviewed-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>