soc/intel/common/block: add bios caching to fast spi module

Add fast_spi_cache_bios_region() that sets up a variable
MTRR as write-protect covering the fast spi BIOS region.

Change-Id: I282c5173cc655004daf16ea2e85423aaded3648d
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/20019
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Subrata Banik <subrata.banik@intel.com>
Reviewed-by: Philippe Mathieu-Daudé <philippe.mathieu.daude@gmail.com>
6 files changed