[media] xc4000: debug message improvements

The following patch makes a few minor changes to the printing
of debug messages, and reporting the tuner status. The 'debug'
module parameter can now be set from 0 to 2 to control the
verbosity of debug messages.

Signed-off-by: Istvan Varga <istvan_v@mailbox.hu>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>