V4L/DVB (11803): xc5000: add support for DVB-T tuning

This patch adds XC5000 supports for DVB-T 6MHz and 8MHz bandwidth.

Signed-off-by: David T.L. Wong <davidtlwong@gmail.com>
Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>