media: v4l2-ctrl: Add layer wise bitrate controls for h264

Adds bitrate control for all coding layers for h264
same as hevc.

Signed-off-by: Dikshita Agarwal <dikshita@codeaurora.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>