xhci: Avoid global symbol pollution with handshake.

Non-static xHCI driver symbols should start with the "xhci_" prefix, in
order to avoid namespace pollution.  Rename the "handshake" function to
"xhci_handshake".

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Reported-by: Ben Hutchings <ben@decadent.org.uk>

drivers/usb/host/xhci-ring.c

@@ -318,7 +318,7 @@ static int xhci_abort_cmd_ring(struct xhci_hcd *xhci)
 	 * seconds), then it should assume that the there are
 	 * larger problems with the xHC and assert HCRST.
 	 */
-	ret = handshake(xhci, &xhci->op_regs->cmd_ring,
+	ret = xhci_handshake(xhci, &xhci->op_regs->cmd_ring,
 			CMD_RING_RUNNING, 0, 5 * 1000 * 1000);
 	if (ret < 0) {
 		xhci_err(xhci, "Stopped the command ring failed, "