[GFS2] Merge gfs2_alloc_meta and gfs2_alloc_data

Thanks to the preceeding patches, the only difference between
these two functions is their name. We can thus merge them
and call the new function gfs2_alloc_block to reflect the
fact that it can allocate either kind of block.

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

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

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

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

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

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