src/cpu/x86/mtrr/earlymtrr: Add clear_all_var_mtrr
Picasso does not define the state of variable MTRRs on boot. Add a
helper function to clear all MTRRs.
BUG=b:
147042464
TEST=Build trembyle
Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: I21b887ce12849a95ddd8f1698028fb6bbfb4a7f6
Reviewed-on: https://review.coreboot.org/c/coreboot/+/40764
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>