Bus Pirate SPI fine tuning.

[Brian Salcedo]

This negates my previous pull-up resistors patch.

Please see http://dangerousprototypes.com/docs/SPI_(binary) for more
information.

This patch adds additional fine tuning parameters for SPI on the Bus
Pirate. If documenting these parameters, please refer the reader to the
Bus Pirate documentation - not flashrom!

The original initialization parameters are retained. (0xb and 0xa
respectively)

Signed-off-by: Brian Salcedo