Revert "xhci: replace xhci_read_64() with readq()"

This reverts commit e8b373326d8efcaf9ec1da8b618556c89bd5ffc4.  Many xHCI
host controllers can only handle 32-bit addresses, and writing 64-bits
at a time causes them to fail.  Reading 64-bits at a time may also cause
them to return 0xffffffff, so revert this commit as well.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index e19fae9..909b32a 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -307,7 +307,7 @@
 		return 0;
 	}
 
-	temp_64 = readq(&xhci->op_regs->cmd_ring);
+	temp_64 = xhci_read_64(xhci, &xhci->op_regs->cmd_ring);
 	if (!(temp_64 & CMD_RING_RUNNING)) {
 		xhci_dbg(xhci, "Command ring had been stopped\n");
 		return 0;
@@ -2865,7 +2865,7 @@
 		/* Clear the event handler busy flag (RW1C);
 		 * the event ring should be empty.
 		 */
-		temp_64 = readq(&xhci->ir_set->erst_dequeue);
+		temp_64 = xhci_read_64(xhci, &xhci->ir_set->erst_dequeue);
 		xhci_write_64(xhci, temp_64 | ERST_EHB,
 				&xhci->ir_set->erst_dequeue);
 		spin_unlock(&xhci->lock);
@@ -2879,7 +2879,7 @@
 	 */
 	while (xhci_handle_event(xhci) > 0) {}
 
-	temp_64 = readq(&xhci->ir_set->erst_dequeue);
+	temp_64 = xhci_read_64(xhci, &xhci->ir_set->erst_dequeue);
 	/* If necessary, update the HW's version of the event ring deq ptr. */
 	if (event_ring_deq != xhci->event_ring->dequeue) {
 		deq = xhci_trb_virt_to_dma(xhci->event_ring->deq_seg,