util/cbfstool: fix buffer over-read

Fix unterminated array.

When looking for a type not specified in filetypes (cbfs.h:204), the
loop in lookup_name_by_type (cbfs_image.c:60) will run into a buffer
over-read.

Found-by: AFL++ 2.64d rev 1317433
Signed-off-by: Philipp Bartsch <phil@grmr.de>
Change-Id: Ib82bb92e82b09fa1e26b9ca34529ec7b98e8f7b1
Reviewed-on: https://review.coreboot.org/c/coreboot/+/41421
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

util/cbfstool/cbfs.h

@@ -210,7 +210,8 @@ static struct typedesc_t filetypes[] unused = {
 	{CBFS_COMPONENT_EFI, "efi"},
 	{CBFS_COMPONENT_STRUCT, "struct"},
 	{CBFS_COMPONENT_DELETED, "deleted"},
-	{CBFS_COMPONENT_NULL, "null"}
+	{CBFS_COMPONENT_NULL, "null"},
+	{0, NULL}
 };
 
 static const struct typedesc_t types_cbfs_hash[] unused = {