V4L/DVB (13313): saa7134: add support for FORCE_TS_VALID mode for mpeg ts input

When FORCE_TS_VALID mode is enabled, the saa713x will accept MPEG TS input
without requiring TS_VALID set high.  This is required for some new boards
to function properly, due to the hardware design implementation.

The configuration is toggled within the board setup configuration.  Boards
that do not have this bit set will function as before with no change.

Signed-off-by: Michael Krufky <mkrufky@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>