[XFS] fix nasty quota hashtable allocation bug

[XFS] fix nasty quota hashtable allocation bug

This git mod: 37f582dc9c34ef763470c67a9f43d64fb3c61d7d
converted to a "greedy" allocation interface, but for the quota hashtables
it switched from allocating XFS_QM_HASHSIZE (nr of elements)
xfs_dqhash_t's to allocating only XFS_QM_HASHSIZE *bytes* - quite a lot
smaller! Then when we converted hsize "back" to nr of elements (the
division line) hsize went to 0. This was leading to oopses when running
any quota tests on the Fedora 8 test kernel, but the problem has been
there for almost a year.

SGI-PV: 968837
SGI-Modid: xfs-linux-melb:xfs-kern:29354a

Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Tim Shimmin <tes@sgi.com>