usb: ehci-mxc: Remove unused 'echi' variable

Since commit c73cee71 (USB: EHCI: remove ehci_port_power() routine), the
'ehci' variable is no longer used, so remove it and fix the following
build warning:

drivers/usb/host/ehci-mxc.c:41:19: warning: unused variable 'ehci' [-Wunused-variable]
Signed-off-by: NFabio Estevam <fabio.estevam@freescale.com>
Acked-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/ehci-mxc.c

@@ -39,8 +39,6 @@ struct ehci_mxc_priv {
 /* called during probe() after chip reset completes */
 static int ehci_mxc_setup(struct usb_hcd *hcd)
 {
-	struct ehci_hcd *ehci = hcd_to_ehci(hcd);
-
 	hcd->has_tt = 1;
 
 	return ehci_setup(hcd);