wimax/i2400m: fix bad assignment of return value in i2400mu_tx_bulk_out

The function was always setting the return value to the amount of
bytes transferred, overwriting the error code in error paths.

Signed-off-by: Inaky Perez-Gonzalez <inaky@linux.intel.com>

drivers/net/wimax/i2400m/usb-fw.c

@@ -157,7 +157,6 @@ retry:
 			result);
 		goto retry;
 	}
-	result = len;
 	if (do_autopm)
 		usb_autopm_put_interface(i2400mu->usb_iface);
 	return result;