google/pit: disable SYSMMU for graphics

It's not needed and it's a potential problem source.

Change-Id: Ic4cafe74e7fc3a9031d852895ad7fd5e5cd64d11
Signed-off-by: Ronald G. Minnich <rminnich@google.com>
Reviewed-on: https://gerrit.chromium.org/gerrit/62279
Commit-Queue: David Hendricks <dhendrix@chromium.org>
Reviewed-by: David Hendricks <dhendrix@chromium.org>
Tested-by: David Hendricks <dhendrix@chromium.org>
Reviewed-on: http://review.coreboot.org/4410
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>
1 file changed