USB: fix problem with usbtmc driver not loading properly

The usbtmc driver forgot to export its device table to userspace.
Without this, it is never loaded properly when such a device is seen by
the system.

Cc: Marcel Janssen <[e-mail]>
Cc: stable <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/class/usbtmc.c

···
 	{ USB_INTERFACE_INFO(USB_CLASS_APP_SPEC, 3, 0), },
 	{ 0, } /* terminating entry */
 };
+MODULE_DEVICE_TABLE(usb, usbtmc_devices);
 
 /*
  * This structure is the capabilities for the device