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>

Makefile

@@ -640,6 +640,9 @@ CONFIG_IT8212 ?= yes
 # Winchiphead CH341A
 CONFIG_CH341A_SPI ?= yes
 
+# Digilent Development board JTAG
+CONFIG_DIGILENT_SPI ?= yes
+
 # Disable wiki printing by default. It is only useful if you have wiki access.
 CONFIG_PRINT_WIKI ?= no
 
@@ -667,6 +670,7 @@ endif
 ifeq ($(CONFIG_ENABLE_LIBUSB1_PROGRAMMERS), no)
 override CONFIG_CH341A_SPI = no
 override CONFIG_DEDIPROG = no
+override CONFIG_DIGILENT_SPI = no
 endif
 ifeq ($(CONFIG_ENABLE_LIBPCI_PROGRAMMERS), no)
 override CONFIG_INTERNAL = no
@@ -934,6 +938,12 @@ PROGRAMMER_OBJS += ch341a_spi.o
 NEED_LIBUSB1 += CONFIG_CH341A_SPI
 endif
 
+ifeq ($(CONFIG_DIGILENT_SPI), yes)
+FEATURE_CFLAGS += -D'CONFIG_DIGILENT_SPI=1'
+PROGRAMMER_OBJS += digilent_spi.o
+NEED_LIBUSB1 += CONFIG_DIGILENT_SPI
+endif
+
 ifneq ($(NEED_SERIAL), )
 LIB_OBJS += serial.o custom_baud.o
 endif