GFS2: Remove i_disksize

With the update of the truncate code, ip->i_disksize and
inode->i_size are merely copies of each other. This means
we can remove ip->i_disksize and use inode->i_size exclusively
reducing the size of a GFS2 inode by 8 bytes.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

diff --cc fs/gfs2/aops.c
Simple merge

diff --cc fs/gfs2/bmap.c
Simple merge

diff --cc fs/gfs2/dir.c
Simple merge

diff --cc fs/gfs2/file.c
Simple merge

diff --cc fs/gfs2/glops.c
Simple merge

diff --cc fs/gfs2/incore.h
Simple merge

diff --cc fs/gfs2/inode.c
Simple merge

diff --cc fs/gfs2/inode.h
Simple merge

diff --cc fs/gfs2/ops_fstype.c
Simple merge

diff --cc fs/gfs2/ops_inode.c
Simple merge

diff --cc fs/gfs2/quota.c
Simple merge

diff --cc fs/gfs2/rgrp.c
Simple merge

diff --cc fs/gfs2/super.c
Simple merge