[media] stv090x: Fix delivery system setting

As sparse complains:
	drivers/media/dvb-frontends/stv090x.c:3471:30: warning: mixing different enum types
	drivers/media/dvb-frontends/stv090x.c:3471:30:     int enum fe_delivery_system  versus
	drivers/media/dvb-frontends/stv090x.c:3471:30:     int enum stv090x_delsys

There's actually an error when setting the delivery system on
stv090x_search(): it is using the DVBv5 macros as if they were
the stv090x ones.

Instead, we should convert between the two namespaces, returning
an error if an unsupported delivery system is requested.

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>