media: tvp5150: fix set_selection rectangle handling

Currently a local copy of sel->r is made and adapted to the hardware
constraints. After the adaption the value is applied to the hardware but
the driver forgot to reflect the adapted value to the user space.

Drop the local copy and work directly on the requested rectangle
instead to fix this.

Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>