ENGR00270802 usb: otg: delete redundant vbus off operation

ENGR00270802 usb: otg: delete redundant vbus off operation

The problem locates at:

	fsl_otg_start_host(fsm, 0);
	if (pdata->wake_up_enable)
		pdata->wake_up_enable(pdata, false);
	otg_drv_vbus(fsm, 0);

fsl_otg_start_host(fsm, 0) internally calls fsl_otg_drv_vbus(), which does
the same thing as otg_drv_vbus(fsm, 0). More critically, we need disable
VBUS wakeup before close VBUS operation, otherwise unexpected VBUS
wakeup will occur. The solution is to remove the call of fsl_otg_drv_vbus()
in fsl_otg_start_host().

Signed-off-by: Peter Chen <peter.chen@freescale.com>