V4L/DVB (3154): TTUSB DEC driver patch roundup

- Collection of patches from Peter Beutner addressing:
- add symbolrates to the DVB-S frontend description
- fix capability flags in DVB-S frontend describtion
- remove some void casts
- disable zig-zag scanning as it makes no sense for DVB-T
- set sensible min_delay value
- return an error for requested filter types the driver can't handle

Signed-off-by: Peter Beutner <p.beutner@gmx.net>
Signed-off-by: Alex Woods <linux-dvb@giblets.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@brturbo.com.br>