fix(bakery_lock): add __unused for clang

is_lock_acquired() function is only used in assert() statements, so when
compiling without asserts, e.g. with DEBUG=0, the function is unused.
this is okay when compiling with gcc because the function is marked as
inline but that doesn't work for clang. let's mark this as __unused to
avoid -Wunused-function warning-as-error.

Change-Id: I93f808fd15f715a65d1bd4f7592affb7997c4bad
Signed-off-by: Okash Khawaja <okash@google.com>

lib/locks/bakery/bakery_lock_normal.c

@@ -83,7 +83,7 @@ static inline void read_cache_op(uintptr_t addr, bool cached)
 }
 
 /* Helper function to check if the lock is acquired */
-static inline bool is_lock_acquired(const bakery_info_t *my_bakery_info,
+static inline __unused bool is_lock_acquired(const bakery_info_t *my_bakery_info,
 				    bool is_cached)
 {
 	/*