The function is only used when CONFIG_PPC_PMAC=y. Adding the attribute
fixes the following warning when building with clang:

block/partitions/mac.c:22:20: error: unused function 'mac_fix_string'
    [-Werror,-Wunused-function]

Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
---
 block/partitions/mac.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/partitions/mac.c b/block/partitions/mac.c
index 621317ac4d59..57483faddaac 100644
--- a/block/partitions/mac.c
+++ b/block/partitions/mac.c

@@ -19,7 +19,7 @@ extern void note_bootable_part(dev_t dev, int part, int goodness);
  * Code to understand MacOS partition tables.
  */
 
-static inline void mac_fix_string(char *stg, int len)
+static inline void __maybe_unused mac_fix_string(char *stg, int len)
 {
 	int i;