gfs2: Don't pack struct lm_lockname

As per a suggestion by Linus, don't pack struct lm_lockname: we did that
because the struct is used as a rhashtable key, but packing tells the
compiler that the 64-bit fields in the struct may be unaligned, causing
it to generate worse code on some architectures.  Instead, rearrange the
fields in the struct so that there is no padding between fields, and
exclude any tail padding from the hash key size.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>