V4L/DVB (8066): cx18: Fix audio mux input definitions for HVR-1600 Line In 2 and FM radio

Fix the cx18-cards.c structures for the HVR-1600 to reflect that audio Line In 2
and FM radio audio go to AIN3 and AIN4 of the CS5345 mux respectively.  Verified
by physical inspection of an HVR-1600MCE, by listening to FM broadcasts with the
HVR-1600MCE, and by comparing with the card definition for a PVR-150 in ivtv.

Signed-off-by: Andy Walls <awalls@radix.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>