GFS2: Improve error handling in inode allocation

A little while back, block allocation was given some improved
error handling which meant that -EIO was returned in the case
of there being a problem in the resource group data. In addition
a message is printed explaning what went wrong and how to fix it.
This extends that error handling so that it also covers inode
allocation too.

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

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

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

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