Patch spi

[zaphoxx]

changes:

• added spi sniffing on bios chip capability (spi_sniffer.pio)
• added hw selection using gpio 14 and 15, currently only 14 is used where 0 --> spi sniff, 1--> original lpc sniff
• vmk header search is changed to check for 9/12 header bytes only
• added a visible 5 second countdown at the beginning as I noticed that at least for the spi sniffing the laptop needs to have been started right before state machine begins. this is probably similar to starting the laptop and then pushing down the pins on the testpad for lpc. i still need to investigate this but as long as the laptop starts within the 5 sec windows it seems to be consistently ok.
• I created another hardware shield with some modifications (additional pin header for test clip, dip switch for mode select and a reset button) I havent uploaded it yet as i first wanted to test the pcb on an actual laptop.

let me know if you have any questions or comments.

[zaphoxx]

new updates have been incorporated; will open a new pull requests.