f2fs: fix macro definition on_f2fs_build_free_nids

The macro on_f2fs_build_free_nids accepts a parameter nmi,
but it was not used, rather the variable nm_i was directly used,
which may be a local variable inside a function that calls the macros.
Signed-off-by: Julian Sun <sunjunchao2870@gmail.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/node.c

@@ -20,7 +20,7 @@
 #include "iostat.h"
 #include <trace/events/f2fs.h>
 
-#define on_f2fs_build_free_nids(nmi) mutex_is_locked(&(nm_i)->build_lock)
+#define on_f2fs_build_free_nids(nm_i) mutex_is_locked(&(nm_i)->build_lock)
 
 static struct kmem_cache *nat_entry_slab;
 static struct kmem_cache *free_nid_slab;