[media] mt2063: remove mt2063_setTune from header

Commit 99ac5412 removed
the function mt2063_setTune() from mt2063.c. Remove it
also from the header file.

Signed-off-by: Danny Kukawka <danny.kukawka@bisect.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>