media: xc5000: Fix get_frequency()

commit a3eec916cbc17dc1aaa3ddf120836cd5200eb4ef upstream.

The programmed frequency on xc5000 is not the middle
frequency, but the initial frequency on the bandwidth range.
However, the DVB API works with the middle frequency.

Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>