V4L/DVB (6651): xc2028: mask off type correctly when searching for standard-specific types

When searching for standard-specific analog firmware, only certain
type bits are valid, much like for DTV.  Mask them off when finding
the firmware to load.

Signed-off-by: Chris Pascoe <c.pascoe@itee.uq.edu.au>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>