usb: dwc3: gadget: prevent DCTL register corruption

If we don't read out the contents of the register
(in order to reinitialize 'reg' variable) we will
be writing unknown contents to the DCTL register
whenever we try to use dwc3_gadget_wakeup() function.
Signed-off-by: NFelipe Balbi <balbi@ti.com>

drivers/usb/dwc3/gadget.c

@@ -1307,6 +1307,7 @@ static int dwc3_gadget_wakeup(struct usb_gadget *g)
 	/* Recent versions do this automatically */
 	if (dwc->revision < DWC3_REVISION_194A) {
 		/* write zeroes to Link Change Request */
+		reg = dwc3_readl(dwc->regs, DWC3_DCTL);
 		reg &= ~DWC3_DCTL_ULSTCHNGREQ_MASK;
 		dwc3_writel(dwc->regs, DWC3_DCTL, reg);
 	}