media: allegro: adjust channel after format change

A format change (i.e. the frame size or the codec) has multiple effects
on a channel:

- The available controls

- The limits of the available controls

- The default encoding options

To avoid scattering the changes all over the driver, add a new function
that goes over the channel and does all required adjustments.

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