[media] xc4000: code cleanup

This is the first of a set of patches that update the original xc4000
sources to my modified version. It removes some unused code, and makes
a few minor formatting changes.

[mchehab@redhat.com: re-add XC_TUNE_ANALOG/XC_TUNE_DIGITAL constants, to avoid compilation breakage]
Signed-off-by: Istvan Varga <istvan_v@mailbox.hu>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>