usb: dwc2: Make dwc2_force_mode() static

Declared dwc2_force_mode() function as static, because it was used
only in core.c file, for fixing sparse error.
Acked-by: NJohn Youn <johnyoun@synopsys.com>
Signed-off-by: NGrigor Tovmasyan <tovmasya@synopsys.com>
Signed-off-by: NFelipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc2/core.c

@@ -611,7 +611,7 @@ void dwc2_force_mode(struct dwc2_hsotg *hsotg, bool host)
  * the force mode. We only need to call this once during probe if
  * dr_mode == OTG.
  */
-void dwc2_clear_force_mode(struct dwc2_hsotg *hsotg)
+static void dwc2_clear_force_mode(struct dwc2_hsotg *hsotg)
 {
 	u32 gusbcfg;