media: pci: saa7146: advertise only those TV standard that are supported

V4L2_STD_ALL advertises more standards than these boards
actually support. This causes a V4L2 compliance issue. Limit
the supported standards to those that are actually implemented.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>