digilent_spi: add a driver for the iCEblink40 development board

This is driver that supports the Lattice iCE40 evaluation kits. On the
board is a SPI flash memory chip labeled ST 25P10VP.

Tested to work read/write/erase with "-p digilent_spi -c M25P10" or
with a patch that resets the part beforehands (in which case it gets
detected as a M25P10-A and is way faster due to paged writes).

Change-Id: I7ffcd9a2db4395816f0e8b6ce6c3b0d8e930c9e6
Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Reviewed-on: https://review.coreboot.org/23338
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
5 files changed