ext2: protect inode changes in the SETVERSION and SETFLAGS ioctls

Unlock mutex after i_flags and i_ctime updates in the EXT2_IOC_SETFLAGS
ioctl.

Use i_mutex in the EXT2_IOC_SETVERSION ioctl to protect i_ctime and
i_generation updates and make the ioctl consistent since i_mutex is
also used in other places to protect timestamps and inode changes.

Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
Signed-off-by: Jan Kara <jack@suse.cz>