fmap: Map full FMAP for verification in fallback path

The rarely-used fallback path for accessing the FMAP without a cache
currently only maps the FMAP header for the initial verify_fmap() call.
This used to be fine when we were just checking the magic number, but
with CBFS verification we may need to hash the entire FMAP.

Since this path is so rarely used anyway and the size difference only
has a practical impact on a few platforms, lets keep things simple and
just always map the whole FMAP.

Change-Id: Ie780a3662bf89637de93a36ce6e23f77fed86265
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/78914
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/lib/fmap.c

@@ -122,7 +122,7 @@ static int find_fmap_directory(struct region_device *fmrd)
 	if (boot == NULL)
 		return -1;
 
-	fmap = rdev_mmap(boot, offset, sizeof(struct fmap));
+	fmap = rdev_mmap(boot, offset, FMAP_SIZE);
 
 	if (fmap == NULL)
 		return -1;