soc/intel/common/block/fast_spi: Refactor ROM caching implementation

This patch removes different implementation to cache the SPI ROM between
early and later boot stage where SPI ROM caching doesn't need even
advanced implementation like `mtrr_use_temp_range()` as SPI ROM ranage
is always mapped to below 4GB hence, simple `set_var_mtrr()` function
can be sufficient without any additional complexity.

BUG=b:225766934
TEST=Calling into `fast_spi_cache_bios_region()` from ramstage is able
to update the temporary variable range MTRRs and showed ~44ms of boot
time savings as below:

Before:
  90:starting to load payload                    1,084,052 (14)
  15:starting LZMA decompress (ignore for x86)   1,084,121 (68)
  16:finished LZMA decompress (ignore for x86)   1,140,742 (56,620)

After:
  90:starting to load payload                    1,090,433 (14)
  15:starting LZMA decompress (ignore for x86)   1,090,650 (217)
  16:finished LZMA decompress (ignore for x86)   1,102,896 (12,245)

Signed-off-by: Subrata Banik <subratabanik@google.com>
Change-Id: I43973b45dc6d032cfcc920eeb36b37fe027e6e8e
Reviewed-on: https://review.coreboot.org/c/coreboot/+/63221
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Nick Vaccaro <nvaccaro@google.com>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

0 files changed, 0 insertions, 0 deletions