media: stv090x: add physical layer scrambling support

This commit uses the new property scrambling_sequence_index
to control PLS.
By default we are using the gold sequence 0 and only gold sequences
expected on the new property.

Please note that all services use PLS, just most with the default
sequence 0 and many demods only support gold 0.

Signed-off-by: Athanasios Oikonomou <athoik@gmail.com>
Acked-by: Ralph Metzler <rjkm@metzlerbros.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>