[media] rtl2832: implement option to bypass slave demod TS

Implement partial PIP mode to carry TS from slave demodulator,
through that master demodulator. RTL2832 demod has TS input
interface to connected another demodulator TS output.

Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>