media: allegro: extract nal value lookup functions to header

The lookup of the h.264 or hevc values for the respective V4L2 controls
is done by the driver that uses the sps/pps generator and not in the
generator. Therefore, it is more intuitive to define these functions
directly in the header and not in the module.

Extract the functions to the headers as static inline functions.

Also simplify the function name and add kernel-doc for the hevc
functions.

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>