[media] stv090x: make sleep/wakeup specific to the demod path

The STV0900 features two demodulator paths in one chip. Thus it is not
possible to use the generic power off function of the chip when sending
one of them to standby. The other path will stop working in that case.

The sleep function now switches off functionality specific to the demod
path. The global stuff is only switched off, when both paths are in
sleep mode. The wakeup function always turns on the global functionality
and then works specific to the path.

Signed-off-by: Andreas Regel <andreas.regel@gmx.de>
Signed-off-by: Oliver Endriss <o.endriss@gmx.de>
Signed-off-by: Manu Abraham <manu@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>