[coreboot] libpayload for ARM with sprinklings of GPL and coreboot code sharing

[mrnuke]

I'll try to be short.

* Usually, ARM payloands need to use SoC specific drivers to access storage 	
    devices.
 * Sometimes coreboot implements the same drivers.

Proposal:
 * Share these drivers between coreboot and libpayload.
 * libpayload is BSD. Have a "[ ] Enable GPL features" config option which 	
    "unlocks" the GPL'd drivers from coreboot.
 * libpayload core remains BSD.
 * coreboot drivers are available to GPL users of libpayload
 * Both the licensing of libpayload-core and coreboot is maintained/respected
 * Makes maintenance easier
 * Makes libpayload relevant in the ARM space

Alex