USB: fsl_qe_udc: Fix muram corruption by disabled endpoints

Before freeing an endpoint's muram memory, we should stop all activity
of the endpoint, otherwise the QE UDC controller might do nasty things
with the muram memory that isn't belong to that endpoint anymore.

The qe_ep_reset() effectively flushes the hardware fifos, finishes all
late transaction and thus prevents the corruption.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>