Add a spi_master interface supporting MediaTek MST9U ISP mode.
Autodetect the bus type via I2C_FUNC_I2C, and use the appropriate
read/write commands, in case the MST9U is attached to smbus.
TEST=Successfully programmed SPI on test hardware.
Change-Id: I24adb14e7b4f7160e1c3ff941774064d5a81e820
Signed-off-by: Neill Corlett <corlett@google.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/61288
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
