usb: gadget: obex: select correct ep descriptors

We where selecting wrong ep descriptors causing
some troubles while sending files over obex interface.

The problem was a typo while usb_find_endpoint() was being
called for HS endpoints.

Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Felipe Balbi <felipe.balbi@nokia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>