V4L/DVB (10165): Add FE_CAN_2G_MODULATION flag to frontends that support DVB-S2

Report to userspace that cx24116 and stv0899 drivers support DVB-S2.

Signed-off by: Klaus Schmidinger <Klaus.Schmidinger@cadsoft.de>

Acked-by: Steven Toth <stoth@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>