linux_spi: Hardcode default spispeed of 2MHz

Leaving the `linux_spi` driver's unknown default is almost never what we
want and resulted in many support requests since Raspbian switched to a
default that is too high for most applications.

Change-Id: I9361b7c1a1ab8900a619b06e1dae14cd87eb56c2
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/30368
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
1 file changed