media: hantro: Support cropping visible area for encoders

Encoders typically operate on macroblocks. Thus their output or coded
resolution is constrained to multiples of macroblocks. For frame sizes
not aligned to macroblocks, cropping is needed to limit the visible
area of the frame.

Add support for cropping on the output (source) side for encoders,
using the selection API.

Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Reviewed-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>