[media] stv090x: Fix some compilation warnings

A few typos at the driver are causing the following warnings:

drivers/media/dvb/frontends/stv090x.c: In function ‘stv090x_start_search’:
drivers/media/dvb/frontends/stv090x.c:1486:27: warning: comparison between ‘enum stv090x_search’ and ‘enum stv090x_delsys’
drivers/media/dvb/frontends/stv090x.c:1487:24: warning: comparison between ‘enum stv090x_search’ and ‘enum stv090x_delsys’
drivers/media/dvb/frontends/stv090x.c: In function ‘stv090x_optimize_track’:
drivers/media/dvb/frontends/stv090x.c:2943:2: warning: case value ‘4’ not in enumerated type ‘enum stv090x_delsys’

The first two are due to the lack of using the delsys types
	STV090x_DVBS1/STV090x_DSS
instead of
	STV090x_SEARCH_DVBS1/STV090x_SEARCH_DSS

The second one is due to the usage of STV090x_UNKNOWN (enum stv090x_modulation)
instead of STV090x_ERROR (enum stv090x_delsys).

Cc: Manu Abraham <abraham.manu@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>