MIPS: SGI-IP27: get rid of volatile and hubreg_t

Replace hub register access with __raw_readq/__raw_writeq and get
rid of hubreg_t completely. Also remove no longer (probably never
used) used defines

Signed-off-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: linux-mips@vger.kernel.org
Cc: linux-kernel@vger.kernel.org