V4L/DVB (3667a): Fix SAP + stereo mode at msp3400

V4L/DVB (3667a): Fix SAP + stereo mode at msp3400

It should be V4L2_TUNER_MODE_LANG1_LANG2. What the code does is check if
we are NTSC and a SAP channel is available. If so, then the msp3400
should switch to standard 0x21 if the user wants to hear the SAP
channel, which is for audio modes LANG2 (aka SAP) and LANG1_LANG2
(bilingual).

In the msp3400 driver STEREO is abused for bilingual in PAL. Bilingual
never worked with NTSC in the past and I decided that I'd better not
use the bad PAL example.

Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>