affs: get rid of affs_sync_super

This patch makes affs stop using the VFS '->write_super()' method along with
the 's_dirt' superblock flag, because they are on their way out.

The whole "superblock write-out" VFS infrastructure is served by the
'sync_supers()' kernel thread, which wakes up every 5 (by default) seconds and
writes out all dirty superblocks using the '->write_super()' call-back.  But the
problem with this thread is that it wastes power by waking up the system every
5 seconds, even if there are no diry superblocks, or there are no client
file-systems which would need this (e.g., btrfs does not use
'->write_super()'). So we want to kill it completely and thus, we need to make
file-systems to stop using the '->write_super()' VFS service, and then remove
it together with the kernel thread.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/affs/bitmap.c

@@ -103,7 +103,7 @@ affs_free_block(struct super_block *sb, u32 block)
 	*(__be32 *)bh->b_data = cpu_to_be32(tmp - mask);
 
 	mark_buffer_dirty(bh);
-	sb->s_dirt = 1;
+	affs_mark_sb_dirty(sb);
 	bm->bm_free++;
 
 	mutex_unlock(&sbi->s_bmlock);
@@ -248,7 +248,7 @@ find_bit:
 	*(__be32 *)bh->b_data = cpu_to_be32(tmp + mask);
 
 	mark_buffer_dirty(bh);
-	sb->s_dirt = 1;
+	affs_mark_sb_dirty(sb);
 
 	mutex_unlock(&sbi->s_bmlock);