spidriver: Add support for the Excamera Labs SPIDriver programmer

This is a SPI hardware interface with a display (https://spidriver.com/),
connected as an FT230X USB serial device at a fixed baud rate of 460800.

Firmware: https://github.com/jamesbowman/spidriver
Protocol: https://github.com/jamesbowman/spidriver/blob/master/protocol.md

Most of the implementation is copied from the Bus Pirate programmer.

Tested with a SPIDriver v2 by reading FM25Q128A flash memory on Linux.

Change-Id: I07b23c1146d4ad3606b54a1e8dc8030cf4ebf57b
Signed-off-by: Simon Arlott <flashrom@octiron.net>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/86411
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Peter Marheine <pmarheine@chromium.org>
Reviewed-by: Anastasia Klimchuk <aklm@chromium.org>

meson.build

@@ -542,6 +542,13 @@ programmer = {
     'srcs'    : files('serprog.c', 'serial.c', custom_baud_c),
     'flags'   : [ '-DCONFIG_SERPROG=1' ],
   },
+  'spidriver' : {
+    'systems' : systems_serial,
+    'groups'  : [ group_serial, group_external ],
+    'srcs'    : files('spidriver.c', 'serial.c', custom_baud_c),
+    'test_srcs' : files('tests/spidriver.c'),
+    'flags'   : [ '-DCONFIG_SPIDRIVER=1' ],
+  },
   'stlinkv3_spi' : {
     'deps'    : [ libusb1 ],
     'groups'  : [ group_usb, group_external ],