media: stkwebcam: fix runtime PM after driver unbind

Since commit c2b7146 ("USB: core: Fix bug caused by duplicate
interface PM usage counter") USB drivers must always balance their
runtime PM gets and puts, including when the driver has already been
unbound from the interface.

Leaving the interface with a positive PM usage counter would prevent a
later bound driver from suspending the device.

Note that runtime PM has never actually been enabled for this driver
since the support_autosuspend flag in its usb_driver struct is not set.

Fixes: c2b7146 ("USB: core: Fix bug caused by duplicate interface PM usage counter")
Cc: stable <stable@vger.kernel.org>
Acked-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20191001084908.2003-5-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/media/usb/stkwebcam/stk-webcam.c

@@ -643,8 +643,7 @@ static int v4l_stk_release(struct file *fp)
 		dev->owner = NULL;
 	}
 
-	if (is_present(dev))
-		usb_autopm_put_interface(dev->interface);
+	usb_autopm_put_interface(dev->interface);
 	mutex_unlock(&dev->lock);
 	return v4l2_fh_release(fp);
 }