usb: serial: zte_ev: move support for ZTE AC2726 from zte_ev back to option

ZTE AC2726 EVDO modem drops ppp connection every minute when driven by
zte_ev but works fine when driven by option. Move the support for AC2726
back to option driver.

Signed-off-by: Dmitry Kunilov <dmitry.kunilov@gmail.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>