GFS2: Make . and .. qstrs constant

Rather than calculating the qstrs for . and .. each time
we need them, its better to keep a constant version of
these and just refer to them when required.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Reviewed-by: Christoph Hellwig <hch@infradead.org>

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

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

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

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

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