usb: xhci: fix build warning

/home/b29397/work/code/git/linus/linux-2.6/drivers/usb/host/xhci-ring.c: In function ‘handle_port_status’:
/home/b29397/work/code/git/linus/linux-2.6/drivers/usb/host/xhci-ring.c:1580: warning: ‘hcd’ may be used uninitialized in this function

Signed-off-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>