V4L/DVB (5381): Dvb-ttpci: Update frontend lock status in transfer mode (bugfix)

In transfer/replay mode the frontend lock status was never updated.
This caused a 'black screen' if VDR switched from transfer mode to
live mode on the same transponder.
Thanks to Marco Schluessler for spotting the problem.

Signed-off-by: Oliver Endriss <o.endriss@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>