vendorcode/cavium: Fix additions to string

The clang compiler is confused about adding integers to strings. Adding
brackets around the macros fixes this.

TEST: BUILD_TIMELESS=1 remains the same.

Change-Id: I2ea17322352d977bf0ec3ee71b14463fa218d07c
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/74541
Reviewed-by: Felix Singer <service+coreboot-gerrit@felixsinger.de>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/vendorcode/cavium/bdk/libbdk-hal/bdk-qlm.c

@@ -58,7 +58,7 @@ BDK_REQUIRE_DEFINE(QLM);
  */
 const char *bdk_qlm_mode_to_cfg_str(bdk_qlm_modes_t mode)
 {
-#define MODE_CASE(m) case m: return #m+13
+#define MODE_CASE(m) case (m): return (#m)+13
     switch (mode)
     {
         MODE_CASE(BDK_QLM_MODE_DISABLED);