[media] Schedule removal of i.MX25 support in mx2_camera.c

Support for i.MX25 in mx2_camera.c has been broken
for a year. Furthermore, i.MX25 video capture HW
doesn't have much in common with i.MX27. A separate
driver would be desirable.

Signed-off-by: Javier Martin <javier.martin@vista-silicon.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>