V4L/DVB (3275): Allow SAA7134 to fall back to AM sound when there is NICAM-L

This patch allows to select AM sound even if NICAM is detected.
Proposed by Alain Frappin

Signed-off-by: Hartmut Hackmann <hartmut.hackmann@t-online.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>