ioatdma: Remove the use of writeq from the ioatdma driver

There's only one now anyway, and it's not in a performance path,
so make it behave the same on 32-bit and 64-bit CPUs.
Signed-off-by: Chris Leech <christopher.leech@intel.com>

drivers/dma/ioatdma.c

@@ -608,13 +608,11 @@ static void ioat_start_null_desc(struct ioat_dma_chan *ioat_chan)
 	list_add_tail(&desc->node, &ioat_chan->used_desc);
 	spin_unlock_bh(&ioat_chan->desc_lock);
 
-#if (BITS_PER_LONG == 64)
-	writeq(desc->phys, ioat_chan->reg_base + IOAT_CHAINADDR_OFFSET);
-#else
-	writel((u32) desc->phys,
+	writel(((u64) desc->phys) & 0x00000000FFFFFFFF,
 	       ioat_chan->reg_base + IOAT_CHAINADDR_OFFSET_LOW);
-	writel(0, ioat_chan->reg_base + IOAT_CHAINADDR_OFFSET_HIGH);
-#endif
+	writel(((u64) desc->phys) >> 32,
+	       ioat_chan->reg_base + IOAT_CHAINADDR_OFFSET_HIGH);
+
 	writeb(IOAT_CHANCMD_START, ioat_chan->reg_base + IOAT_CHANCMD_OFFSET);
 }