udf: stop using s_dirt

The UDF file-system does not need the 's_dirt' superblock flag because it does
not define the 'write_super()' method. This flag was set to 1 in few places and
set to 0 in '->sync_fs()' and was basically useless. Stop using it because it
is on its way out.

Signed-off-by: Artem Bityutskiy <[e-mail]>
Signed-off-by: Jan Kara <[e-mail]>

fs/udf/super.c

···
 	sb->s_op = &udf_sb_ops;
 	sb->s_export_op = &udf_export_ops;
 
-	sb->s_dirt = 0;
 	sb->s_magic = UDF_SUPER_MAGIC;
 	sb->s_time_gran = 1000;
 
···
 	struct va_format vaf;
 	va_list args;
 
-	/* mark sb error */
-	if (!(sb->s_flags & MS_RDONLY))
-		sb->s_dirt = 1;
-
 	va_start(args, fmt);
 
 	vaf.fmt = fmt;
···
 		 * the buffer for IO
 		 */
 		mark_buffer_dirty(sbi->s_lvid_bh);
-		sb->s_dirt = 0;
 		sbi->s_lvid_dirty = 0;
 	}
 	mutex_unlock(&sbi->s_alloc_mutex);

fs/udf/udfdecl.h

···
 	WARN_ON_ONCE(((struct logicalVolIntegrityDesc *)
 		     bh->b_data)->integrityType !=
 		     cpu_to_le32(LVID_INTEGRITY_TYPE_OPEN));
-	sb->s_dirt = 1;
 	UDF_SB(sb)->s_lvid_dirty = 1;
 }
 extern u64 lvid_get_unique_id(struct super_block *sb);