amd_spi100: Implement memory-mapped reads

Query the RomRange2 register for the memory range (usually top below 4G)
and try to map that. Reads outside this range will still be served via
the command engine.

Change-Id: I21aa67d550ccda0f55a9cf3ff14545a881624d11
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/72583
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
3 files changed