V4L/DVB (9272): mxl5005s: Bug fix stopped DVB-T from working the second time around.

Jose reported:

I am using a Avermedia Volar X with af9015 driver(DVB-T).

The first time you use the card, first call reconfigure with MXL_QAM,
and when tune DVB-T it calls reconfigure with MXL_DVBT. But if you close
the frontend and open again, it calls reconfigure with MXL_QAM, but not
call reconfigure with MXL_DVBT because state->current_mode don't change
(is MXL_DVBT).

Signed-off-by: Jose Alberto Reguero <jareguero@telefonica.net>
Signed-off-by: Steven Toth <stoth@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>