soc/intel/common/fast_spi: Add support for configuring MTRRs

This change enables caching for extended BIOS region.
Currently, caching is enabled for the standard BIOS region
upto a maximum of 16MiB using fast_spi_cache_bios_region,
used the same function to add the support for caching for
extended BIOS region as well.

Changes include:
1. Add a new helper function fast_spi_cache_ext_bios_window()
which calls fast_spi_ext_bios_cache_range() which calls
fast_spi_get_ext_bios_window() to get details about the
extended BIOS window from the boot media map and checks for
allignment and set mtrr.
2. Make a call to fast_spi_cache_ext_bios_region() from
fast_spi_cache_bios_region ().
3. Add new helper function fast_spi_cache_ext_bios_postcar()
which does caching ext BIOS region in postcar similar to 1.
4. If the extended window is used, then it enables caching
for this window similar to how it is done for the standard
window.

BUG=b:171534504

Signed-off-by: Srinidhi N Kaushik <srinidhi.n.kaushik@intel.com>
Change-Id: I9711f110a35a167efe3a4c912cf46c63c0812779
---
M src/soc/intel/common/block/fast_spi/fast_spi.c
M src/soc/intel/common/block/include/intelblocks/fast_spi.h
M src/soc/intel/common/block/systemagent/memmap.c
3 files changed, 60 insertions(+), 0 deletions(-)