media: coda: disable BWB only while decoding on CODA 960

Disabling the BWB works around hangups observed while decoding. Since no
issues have been observed while encoding, and disabling BWB also reduces
encoding performance, reenable it for encoding.

Fixes: 89ed025d

 ("[media] coda: disable BWB for all codecs on CODA 960")

Reported-by: Ian Arkver <ian.arkver.dev@gmail.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Tested-by: Ian Arkver <ian.arkver.dev@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>