media: coda: remove definition of CODA_STD_MJPG

According to i.MX VPU API Reference Manuals the MJPG video codec is
referenced to by number 7, not 3.

Also Philipp pointed out that this value is only meant to fill in
CMD_ENC_SEQ_COD_STD for encoding, only on i.MX53. It was never written
to any register, and even if defined correctly, wouldn't be needed
for i.MX6.

So avoid confusion and remove this definition.

Signed-off-by: Martin Kepplinger <martink@posteo.de>
Acked-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>