[media] DiSEqC bug fixed for stv0288 based interfaces

Fixed problem with DiSEqC communication. The message was wrongly modulated,
so the DiSEqC switch was not work.

This patch fixes DiSEqC messages, simple tone burst and tone on/off.
I verified it with osciloscope against the DiSEqC documentation.

Interface: PCI DVB-S TV tuner TeVii S420
Kernel: 2.6.32-24-generic (UBUNTU 10.4)

Signed-off-by: Josef Pavlik <josef@pavlik.it>
Tested-by: Malcolm Priestley <tvboxspy@gmail.com>
Cc: Igor M. Liplianin <liplianin@me.by>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>