Revert commit 
0555659d63c285ceb7ead3115532e1b71b0f27a7 from 2.6.22-rc1.
The dma_set_mask call somehow failed on a PowerMac G5, PPC64:
http://lkml.org/lkml/2007/8/1/344
Should there ever occur a DMA mapping beyond the physical DMA range, a
proper SBP-2 firmware will report transport errors.  So let's leave it
at that.
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Tested-by: Olaf Hering <olh@suse.de>
                        SBP2_ERR("failed to register lower 4GB address range");
                        goto failed_alloc;
                }
-#else
-               if (dma_set_mask(hi->host->device.parent, DMA_32BIT_MASK)) {
-                       SBP2_ERR("failed to set 4GB DMA mask");
-                       goto failed_alloc;
-               }
 #endif
        }