xhci: add & use xhci_kick_epctx()

xhci_kick_epctx is a xhci_kick_ep variant which takes an XHCIEPContext
as input instead of slotid and epid.  So in case we have a XHCIEPContext
at hand at the callsite we can just pass it directly.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 1474965172-30321-7-git-send-email-kraxel@redhat.com