media: dvb-frontends/stv0367: remove QAM_AUTO from ddb_fe_ops

Since the cab_* codepath doesn't recognize QAM_AUTO, don't announce that
it is supported when it really isn't. Fixes ie. w_scan from
unconditionally using QAM_AUTO on DVB-C scans.

Signed-off-by: Daniel Scheller <d.scheller@gmx.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>