staging: dwc2: refactor dwc2_host_complete()

The parameters to dwc2_host_complete() didn't make much sense.
The 'context' parameter always came from the ->priv member of the
'dwc2_urb' parameter, and both of those always came from a struct
dwc2_qtd. So just pass in the struct dwc2_qtd instead.

This also allows us to null out the dwc2_qtd->urb member after it
is freed, which the calling code forgot to do in several places,
causing random driver crashes from dereferencing the freed pointer.

This also requires the calls to dwc2_hc_handle_tt_clear() to be
moved before the calls to dwc2_host_complete(), otherwise that
routine would do nothing because dwc2_qtd->urb has already been
freed.

Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Tested-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>