usb: gadget: uvc: add uvcg_warn macro

We only have uvcg_dbg, uvcg_info, and uvcg_err, so add uvcg_warn macro
to print gadget device name and function name along with format.
Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/gadget/function/uvc.h

@@ -56,6 +56,8 @@ extern unsigned int uvc_gadget_trace_param;
 	dev_dbg(&(f)->config->cdev->gadget->dev, "%s: " fmt, (f)->name, ##args)
 #define uvcg_info(f, fmt, args...) \
 	dev_info(&(f)->config->cdev->gadget->dev, "%s: " fmt, (f)->name, ##args)
+#define uvcg_warn(f, fmt, args...) \
+	dev_warn(&(f)->config->cdev->gadget->dev, "%s: " fmt, (f)->name, ##args)
 #define uvcg_err(f, fmt, args...) \
 	dev_err(&(f)->config->cdev->gadget->dev, "%s: " fmt, (f)->name, ##args)