stv090x/stv6110x improvements and bug fixes

Hi,

some time ago, I made some improvements and fixed some bugs in the stv090x and stv6110x frontend drivers. These include:

- increased search range on STV090x based on symbol rate
- fixed some STV090x register definitions and typos
- fix STR and SNR calculation and normalize the value into the 0..0xFFFF range
- fixed STV6110x r divider calculation when setting frequency
- first disable DVB-S and DVB-S2 mode before enabling it again for automatic search
- fix calculation of AGC2 values
- corrections of several register values
- several blind scan related fixes

They were available since about two months and tested successfully using TT S2-1600 card by me and other people from vdrportal.de. I made them public in my repository available at http://powarman.dyndns.org/hg/v4l-dvb

Regards
Andreas