usb: disable previously enabled endpoint before re-enabling

When switching between alternate settings of an interface, it is
currently possible to call set_endpoint() multiple times on an endpoint
without first calling reset_endpoint(). For these situations, it is
beneficial to track endpoints for which set_endpoint() has previously
been called, and then reset them to properly terminate any transfers,
and to return the HAL to the correct state

Signed-off-by: Milind Paranjpe <mparanjpe@yahoo.com>