[media] xc5000: better name the functions

xc5000_set_params() is a bad name for a function that
handles only digital TV. Rename it to xc5000_set_digital_params(),
and proper name the generic function that works for both
digital and analog.

No functional changes.

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