media: coda: add read-only h.264 decoder profile/level controls

The decoder profile/level controls initially can be used to determine
supported profiles and levels. The values are set for a given stream
once the headers are parsed.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>