media: coda: set MPEG-4 encoder class register

Explicitly set MPEG-4 encoder class register instead of relying on the
default value of 0.

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@s-opensource.com>