[media] dvb: replace SYS_DVBC_ANNEX_AC by the right delsys

SYS_DVBC_ANNEX_AC is an alias for SYS_DVBC_ANNEX_A. However,
the first one is incorrect, as not all devices support both.
So, replace its occurrences by the proper value (either
SYS_DVBC_ANNEX_A or both SYS_DVBC_ANNEX_A and SYS_DVBC_ANNEX_C).

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>