[media] stv090x: add an extra protetion against buffer overflow

[media] stv090x: add an extra protetion against buffer overflow

As pointed by smatch:
	drivers/media/dvb-frontends/stv090x.c:2787 stv090x_optimize_carloop() error: buffer overflow 'car_loop_apsk_low' 11 <= 13
	drivers/media/dvb-frontends/stv090x.c:2789 stv090x_optimize_carloop() error: buffer overflow 'car_loop_apsk_low' 11 <= 13
	drivers/media/dvb-frontends/stv090x.c:2791 stv090x_optimize_carloop() error: buffer overflow 'car_loop_apsk_low' 11 <= 13
	drivers/media/dvb-frontends/stv090x.c:2793 stv090x_optimize_carloop() error: buffer overflow 'car_loop_apsk_low' 11 <= 13
	drivers/media/dvb-frontends/stv090x.c:2795 stv090x_optimize_carloop() error: buffer overflow 'car_loop_apsk_low' 11 <= 13

The situation of a buffer overflow won't happen, in practice,
with the current values of car_loop table. Yet, the entire logic
that checks for those registration values is too complex. So,
better to add an explicit check, just in case someone changes
the car_loop tables causing a buffer overflow by mistake.

This also helps to remove several smatch warnings, with is good.

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