usb: dwc3: gadget: return error if command sent to DGCMD register fails

commit 891b1dc0 upstream.

We need to return error to caller if command is not sent to
controller succesfully.
Signed-off-by: Subbaraya Sundeep Bhatta <sbhatta@xilinx.com>
Fixes: b09bb642 (usb: dwc3: gadget: implement Global Command support)
Signed-off-by: Felipe Balbi <balbi@ti.com>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

drivers/usb/dwc3/gadget.c

@@ -376,6 +376,8 @@ int dwc3_send_gadget_generic_command(struct dwc3 *dwc, int cmd, u32 param)
 		if (!(reg & DWC3_DGCMD_CMDACT)) {
 			dev_vdbg(dwc->dev, "Command Complete --> %d\n",
 					DWC3_DGCMD_STATUS(reg));
+			if (DWC3_DGCMD_STATUS(reg))
+				return -EINVAL;
 			return 0;
 		}