media: allegro: initialize bitrate using v4l2_ctrl

As the driver now uses the v4l2-ctrls to setup the channel, there is no
need to explicitly set the bitrate. The initial bitrate is now set via
the same path as if it is set from userspace using the v4l2-ctrl.

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>