[media] dvb: get rid of enum dmx_success

[media] dvb: get rid of enum dmx_success

This enum is not actually used anymore. The only value used from
the enum is DMX_OK, passed as a parameter on two callbacks.

Yet, this value is not used anywhere. So, just remove it.

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