Bind only modem AT command endpoint to option module.

commit 15b2f320 upstream.

Network interface is handled by upcoming gt_b3730 module.

Removed "GT-B3710" from comment, it is another modem with another USB ID.

Signed-off-by: Marius B. Kotsbak <marius@kotsbak.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>