media: allegro: create new struct for channel parameters

Add a new struct for the channel parameters that is contained in the
CREATE_CHANNEL message. This is in preparation for newer firmwares that
pass the channel parameters in a dedicated buffer instead of embedding
the parameters into the CREATE_CHANNEL message.

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>