usb: dwc3: fix post-increment

Use pre-increment and set -ETIMEDOUT correctly.
Signed-off-by: NJanusz Dziedzic <januszx.dziedzic@linux.intel.com>
Signed-off-by: NFelipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc3/gadget.c

@@ -214,7 +214,7 @@ int dwc3_send_gadget_generic_command(struct dwc3 *dwc, unsigned cmd, u32 param)
 				ret = -EINVAL;
 			break;
 		}
-	} while (timeout--);
+	} while (--timeout);
 
 	if (!timeout) {
 		ret = -ETIMEDOUT;