src/lib: Add Kconfig option for SPD cache in FMAP

Currently, the option to cache DIMM SPD data in an FMAP region
is closely coupled to a single board (google/hatch) and requires
a custom FMAP to utilize.

Loosen this coupling by introducing a Kconfig option which adds
a correctly sized and aligned RW_SPD_CACHE region to the default FMAP.
Add a Kconfig option for the region name, replacing the existing hard-
coded instance in spd_cache.h. Change the inclusion of spd_cache.c to
use this new Kconfig, rather than the board-specific one currently used.
Lastly, have google/hatch select the new Kconfig when appropriate to
ensure no change in current functionality.

Test: build/boot WYVERN google/hatch variant with default FMAP, verify
FMAP contains RW_SPD_CACHE, verify SPD cache used via cbmem log.

Also tested on an out-of-tree Purism board.

Change-Id: Iee0e7acb01e238d7ed354e3dbab1207903e3a4fc
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/48520
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/Makefile.inc b/Makefile.inc
index 90280df..90c2494 100644
--- a/Makefile.inc
+++ b/Makefile.inc
@@ -966,6 +966,16 @@
 FMAP_SMMSTORE_ENTRY :=
 endif
 
+ifeq ($(CONFIG_SPD_CACHE_IN_FMAP),y)
+FMAP_SPD_CACHE_BASE := $(call int-align, $(FMAP_CURRENT_BASE), 0x4000)
+FMAP_SPD_CACHE_SIZE := $(call int-multiply, $(CONFIG_DIMM_MAX) $(CONFIG_DIMM_SPD_SIZE))
+FMAP_SPD_CACHE_SIZE := $(call int-align, $(FMAP_SPD_CACHE_SIZE), 0x1000)
+FMAP_SPD_CACHE_ENTRY := $(CONFIG_SPD_CACHE_FMAP_NAME)@$(FMAP_SPD_CACHE_BASE) $(FMAP_SPD_CACHE_SIZE)
+FMAP_CURRENT_BASE := $(call int-add, $(FMAP_SPD_CACHE_BASE) $(FMAP_SPD_CACHE_SIZE))
+else
+FMAP_SPD_CACHE_ENTRY :=
+endif
+
 #
 # X86 FMAP region
 #
@@ -1042,6 +1052,7 @@
 	    -e "s,##CONSOLE_ENTRY##,$(FMAP_CONSOLE_ENTRY)," \
 	    -e "s,##MRC_CACHE_ENTRY##,$(FMAP_MRC_CACHE_ENTRY)," \
 	    -e "s,##SMMSTORE_ENTRY##,$(FMAP_SMMSTORE_ENTRY)," \
+	    -e "s,##SPD_CACHE_ENTRY##,$(FMAP_SPD_CACHE_ENTRY)," \
 	    -e "s,##CBFS_BASE##,$(FMAP_CBFS_BASE)," \
 	    -e "s,##CBFS_SIZE##,$(FMAP_CBFS_SIZE)," \
 		$(DEFAULT_FLASHMAP) > $@.tmp