GFS2: Clean up duplicated setattr code

While preparing the last patch I noticed that the gfs2_setattr_simple
code had been duplicated into two other places. This patch updates
those to call gfs2_setattr_simple rather than open coding it.

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

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

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