media: allegro: add config blob for channel

Firmware versions >= 2019.2 do not configure the channel via the mailbox
interface anymore, but use a separate chunk of memory that is only
referenced by the message. As the configuration must be in a format that
is understood by the firmware and this format can change between
firmware versions, handle it similar to the message and treat is as a
blob.

In order to support both methods in the driver, always use a separate
blob for the channel configuration and copy that blob into the mailbox
if the firmware requires it and otherwise reference it.

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>