usbtty: init endpoints prior to startup events

On some usb device controllers (pxa) the endpoint configuration must be programmed prior to enable it.

Signed-off-by: Stefan Herbrechtsmeier <sherbrec@cit-ec.uni-bielefeld.de>
CC: Marek Vasut <marek.vasut@gmail.com>
CC: Remy Bohmer  <linux@bohmer.net>