ext3: Use bitops to read/modify EXT3_I(inode)->i_state

At several places we modify EXT3_I(inode)->i_state without holding i_mutex
(ext3_release_file, ext3_bmap, ext3_journalled_writepage, ext3_do_update_inode,
...). These modifications are racy and we can lose updates to i_state. So
convert handling of i_state to use bitops which are atomic.

Signed-off-by: Jan Kara <jack@suse.cz>