btrfs: rename bitmap_set_bits() -> btrfs_bitmap_set_bits()

bitmap_set_bits() does not start with the FS' prefix and may collide
with a new generic helper one day. It operates with the FS-specific
types, so there's no change those two could do the same thing.
Just add the prefix to exclude such possible conflict.
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Acked-by: David Sterba <dsterba@suse.com>
Reviewed-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

fs/btrfs/free-space-cache.c

@@ -1911,9 +1911,9 @@ static inline void bitmap_clear_bits(struct btrfs_free_space_ctl *ctl,
 		ctl->free_space -= bytes;
 }
 
-static void bitmap_set_bits(struct btrfs_free_space_ctl *ctl,
-			    struct btrfs_free_space *info, u64 offset,
-			    u64 bytes)
+static void btrfs_bitmap_set_bits(struct btrfs_free_space_ctl *ctl,
+				  struct btrfs_free_space *info, u64 offset,
+				  u64 bytes)
 {
 	unsigned long start, count, end;
 	int extent_delta = 1;
@@ -2249,7 +2249,7 @@ static u64 add_bytes_to_bitmap(struct btrfs_free_space_ctl *ctl,
 
 	bytes_to_set = min(end - offset, bytes);
 
-	bitmap_set_bits(ctl, info, offset, bytes_to_set);
+	btrfs_bitmap_set_bits(ctl, info, offset, bytes_to_set);
 
 	return bytes_to_set;