V4L/DVB (7343): msp3400: fix SECAM D/K handling

The 6.5 MHz carrier was interpreted as SECAM-L even if SECAM-D/K was
selected.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>