soc/amd/common/memmap: add comment about types in memmap_early_dram

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Reported-by: Angel Pons <th3fanbus@gmail.com>
Change-Id: I295bfcb05571492adbe81ffc579a835be4abffe1
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50370
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-by: Raul Rangel <rrangel@chromium.org>

src/soc/amd/common/block/include/amdblocks/memmap.h

@@ -9,6 +9,7 @@
 DECLARE_REGION(early_reserved_dram)
 
 struct memmap_early_dram {
+	/* fixed size types, so the layout in CBMEM won't change for 32 vs. 64 bit stages */
 	uint32_t base;
 	uint32_t size;
 };