media: allegro: add support for allegro firmware 2019.2

Encode messages as necessary for the firmware 2019.2 and, thus, support
the more recent firmware version in the driver, too.

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>