All these variables are only used in the files they are defined in, so
they can be made static.

Change-Id: I1e55138adef540e9d3a2237aa5b289cb338c0608
Signed-off-by: Jacob Garber <jgarber1@ualberta.ca>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/33747


Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>