Fix crystal oscilator define and clock init 8mhz VS 12 Mhz

[fishpepper]

As found out in #1, both transmitters have a 8Mhz crystal. The SYSCLK define in the makefile assumes 12MHz. I need to investigate why this is working correctly with the 12.000000 value in the makefile. All timings are correct (9ms frame time for example). Maybe i messed up the sys clock initializing somehow so that it assumes 8mhz input. I will have to take a close look.

[rav-rav]

I've spent hours to find out why my serial output was at 79000 baud instead of 115200.
Default value is 8MHz. Maybe you've build /device/* before adjusting the value in your Makefile?
Make clean does not remove those files.