Instead of per-model tests all over the code, use some parameters
at the board entries to describe the model variants for:
	- devices with 417 MPEG encoder;
	- devices that use external AV;
	- devices where vbi VANC endpoint doesn't work;
	- devices with xc5000 that require different IF
	  initialization (and probably will cover also
	  xc3028).
	- devices with xceive tuner that require a reset
	  during init.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>