ch347_spi: Add simple `spispeed` parameter

Add a programmer parameter `spispeed` that accepts a frequency in kHz
like it's done for other drivers. The frequency will be rounded down
to the closest possible divisor setting.

Change-Id: Ifa05b95f723dba81bdcc7015dcdf557af5f2e0a8
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/73153
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nicholas Chin <nic.c3.14@gmail.com>
2 files changed