ARM: 7796/1: scsi: Use dma_max_pfn(dev) helper for bounce_limit calculations

DMA bounce limit is the maximum direct DMA'able memory beyond which
bounce buffers has to be used to perform dma operations. SCSI driver
relies on dma_mask but its calculation is based on max_*pfn which
don't have uniform meaning across architectures. So make use of
dma_max_pfn() which is expected to return the DMAable maximum pfn
value across architectures.

Cc: linux-scsi@vger.kernel.org
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

drivers/scsi/scsi_lib.c

@@ -1684,7 +1684,7 @@ u64 scsi_calculate_bounce_limit(struct Scsi_Host *shost)
 
 	host_dev = scsi_get_device(shost);
 	if (host_dev && host_dev->dma_mask)
-		bounce_limit = *host_dev->dma_mask;
+		bounce_limit = dma_max_pfn(host_dev) << PAGE_SHIFT;
 
 	return bounce_limit;
 }