btrfs: Make btrfs_(set|clear)_header_flag return void

From the introduction of btrfs_(set|clear)_header_flag, there is no
usage of its return value.  So just make it return void.
Reviewed-by: NNikolay Borisov <nborisov@suse.com>
Signed-off-by: NQu Wenruo <wqu@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/ctree.h

@@ -2163,18 +2163,16 @@ static inline int btrfs_header_flag(const struct extent_buffer *eb, u64 flag)
 	return (btrfs_header_flags(eb) & flag) == flag;
 }
 
-static inline int btrfs_set_header_flag(struct extent_buffer *eb, u64 flag)
+static inline void btrfs_set_header_flag(struct extent_buffer *eb, u64 flag)
 {
 	u64 flags = btrfs_header_flags(eb);
 	btrfs_set_header_flags(eb, flags | flag);
-	return (flags & flag) == flag;
 }
 
-static inline int btrfs_clear_header_flag(struct extent_buffer *eb, u64 flag)
+static inline void btrfs_clear_header_flag(struct extent_buffer *eb, u64 flag)
 {
 	u64 flags = btrfs_header_flags(eb);
 	btrfs_set_header_flags(eb, flags & ~flag);
-	return (flags & flag) == flag;
 }
 
 static inline int btrfs_header_backref_rev(const struct extent_buffer *eb)