V4L/DVB (9522): Increase number of SAA7134 devices supported in a system

The SAA7134 device driver currently only supports 8 such devices in a
system. This is too small for many surveillance applications. This
patch increases the number to 32.

Signed-off-by: Alan McIvor <alan.mcivor@reveal.co.nz>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>