media: rkisp1: isp: Add the enum_frame_size ioctl

Implement the VIDIOC_SUBDEV_ENUM_FRAME_SIZE ioctl for the isp entity,
check if the mbus code is valid for the given pad.
This call is not available for the parameter or metadata pads of the
RkISP1.

Signed-off-by: Sebastian Fricke <sebastian.fricke.linux@gmail.com>
Acked-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Acked-by: Helen Koike <helen.koike@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>