vfs: Rename fsync_super() to sync_filesystem() (version 4)

Rename the function so that it better describe what it really does. Also
remove the unnecessary include of buffer_head.h.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 4b6a3b9..3a6d4fb 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -204,7 +204,7 @@
 {
 	struct super_block *sb = get_super(bdev);
 	if (sb) {
-		int res = fsync_super(sb);
+		int res = sync_filesystem(sb);
 		drop_super(sb);
 		return res;
 	}
@@ -246,7 +246,7 @@
 		sb->s_frozen = SB_FREEZE_WRITE;
 		smp_wmb();
 
-		fsync_super(sb);
+		sync_filesystem(sb);
 
 		sb->s_frozen = SB_FREEZE_TRANS;
 		smp_wmb();