media: v4l2-rect.h: add enclosed rectangle helper

Add a helper function to check if one rectangle is enclosed inside
another.

Signed-off-by: Benoit Parrot <bparrot@ti.com>
Acked-by: Andrzej Pietrasiewicz <andrzejtp2010@gmail.com>
Reviewed-by: Lad Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>