media: camera-mx2: Remove unused header file

The imx27/imx25 camera driver has been removed a long time ago,
so get rid of this unused header file.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>