[media] lgdt3305: add support for fixed tp clock mode

Add support for controlling TP clock mode for VSB and QAM annex-B/C mode.
Gated clock mode is the default value, and does not support QAM annex-C.
The patch enables setting this control to fixed clock mode.

Signed-off-by: Michael Ira Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>