V4L/DVB (3502): Saa7134: make unsupported secondary decoder message generic

There are already some supported devices that contain two
saa713x chips on-board, where only one of these chips is
currently functional in the driver.
We are already printing a warning message for the second
saa7134 decoder in SAA7134_BOARD_AVERMEDIA_A169_B. This
patch alters that case to make it generic, so that other
cards in the same situation can use it.

Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>