V4L/DVB (5633): Tuv1236d: move rf input switching code into dvb-pll

This patch removes duplicate code from cx88-dvb and saa7134-dvb that handles
rf input switching for the TUV1236d tuner.

The functionality is added to dvb-pll, where all the other code that 
handles the TUV1236d is kept.

Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>