usbip: tools: Fix detach_port() invalid port error path

The detach_port() doesn't return error
when detach is attempted on an invalid port.

Fixes: 40ecdeb1a187 ("usbip: usbip_detach: fix to check for invalid ports")
Cc: [e-mail]
Reviewed-by: Hongren Zheng <[e-mail]>
Reviewed-by: Shuah Khan <[e-mail]>
Signed-off-by: Zongmin Zhou <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

tools/usb/usbip/src/usbip_detach.c

···
 	}
 
 	if (!found) {
+		ret = -1;
 		err("Invalid port %s > maxports %d",
 			port, vhci_driver->nports);
 		goto call_driver_close;