mtrr: honor IORESOURCE_WRCOMB

All resources that set the IORESOURCE_WRCOMB attribute which are
also marked as IORESOURCE_PREFETCH will have a MTRR set up that
is of the write-combining cacheable type. The only resources on
x86 that can be set to write-combining are prefetchable ones.

Change-Id: Iba7452cff3677e07d7e263b79982a49c93be9c54
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/2892
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
1 file changed