FX2: Increase reset pulse length to ensure reset works

This should fix issues where the SI4010 didn't reset. Especially
happend when using long wires.
Document the resistors that should be used on the C2CK and C2D wires
C2 BUS: Added FTDI FT232R based bus master support

Added support for the FTDI FT232R chip as C2 bus master. Also some minor
fixes to the c2 bus abstraction layer code.