ext4: make function ‘ext4_getfsmap_find_fixed_metadata’ static

Since function ‘ext4_getfsmap_find_fixed_metadata’ can be made static,
make it so. Remove the following gcc warning (W=1):

  fs/ext4/fsmap.c:405:5: warning: no previous prototype for ‘ext4_getfsmap_find_fixed_metadata’ [-Wmissing-prototypes]
Signed-off-by: Mathieu Malaterre <malat@debian.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/fsmap.c

@@ -402,8 +402,8 @@ static void ext4_getfsmap_free_fixed_metadata(struct list_head *meta_list)
 }
 
 /* Find all the fixed metadata in the filesystem. */
-int ext4_getfsmap_find_fixed_metadata(struct super_block *sb,
-				      struct list_head *meta_list)
+static int ext4_getfsmap_find_fixed_metadata(struct super_block *sb,
+					     struct list_head *meta_list)
 {
 	struct ext4_group_desc *gdp;
 	ext4_group_t agno;