[media] cx231xx: Don't let an interface number to go past the array

On some newer boards, like HVR-930C HD, the information at
the PCB tables are sometimes higher than the ones actually
available on the device. That causes the probing code to
go past the interfaces array.

Add checks to the interface number before going past the
array.

Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>