MIPS: SGI-IP22: provide missing dma_mask/coherent_dma_mask

Set dma_masks for SGIWD93 and SGISEEQ otherwise DMA allocations fails
and causes not working SCSI/ethernet.

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