soc/intel/common/fast_spi: Add extended decode window support

This change enables support for configuration of extended BIOS
region decode window. This configuration needs to be performed
as early as possible in the boot flow. This is required to
ensure that any access to the SPI flash region below 16MiB in
coreboot is decoded correctly. The configuration for the extended
BIOS window if required is done as part of fast_spi_early_init().

Changes include:
1. Make a call to fast_spi_enable_ext_bios() before the bus master
and memory space is enabled for the fast SPI controller.
2. Added a helper function fast_spi_enable_ext_bios() which calls
fast_spi_get_ext_bios_window() to get details about the extended
BIOS window from the boot media map.
3. Depending upon the SPI flash device used by the mainboard and
the size of the BIOS region in the flashmap, this function will
have to perform this additional configuration only if the BIOS
region is greater than 16MiB
4. Adddditionally, set up the general purpose memory range
registers in DMI.

BUG=b:171534504

Signed-off-by: Srinidhi N Kaushik <srinidhi.n.kaushik@intel.com>
Change-Id: Idafd8be0261892122d0b5a95d9ce9d5604a10cf2
---
M src/soc/intel/common/block/fast_spi/fast_spi.c
M src/soc/intel/common/block/fast_spi/fast_spi_def.h
2 files changed, 60 insertions(+), 0 deletions(-)