usb: omap_control_usb: fix compile warning

When CONFIG_OMAP_CONTROL_USB isn't enabled,
there's a compile warning stating that a
particular function isn't a prototype.

Fix it.
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/usb/omap_control_usb.h

@@ -70,7 +70,7 @@ extern void omap_control_usb3_phy_power(struct device *dev, bool on);
 extern void omap_control_usb_set_mode(struct device *dev,
 	enum omap_control_usb_mode mode);
 #else
-static inline struct device *omap_get_control_dev()
+static inline struct device *omap_get_control_dev(void)
 {
 	return ERR_PTR(-ENODEV);
 }