usb: chipidea: host: fix NULL ptr dereference during shutdown

After commit b09b5224 ("usb: chipidea: implement platform shutdown
callback") and commit 43a40457 ("usb: chipidea: host: set host to
be null after hcd is freed") a NULL pointer dereference is caused
on i.MX23 during shutdown. So ensure that role is set to CI_ROLE_END and
we finish interrupt handling before the hcd is deallocated. This avoids
the NULL pointer dereference.
Suggested-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Fixes: b09b5224 ("usb: chipidea: implement platform shutdown callback")
Signed-off-by: Peter Chen <peter.chen@nxp.com>

drivers/usb/chipidea/host.c

@@ -188,6 +188,8 @@ static void host_stop(struct ci_hdrc *ci)
 
 	if (hcd) {
 		usb_remove_hcd(hcd);
+		ci->role = CI_ROLE_END;
+		synchronize_irq(ci->irq);
 		usb_put_hcd(hcd);
 		if (ci->platdata->reg_vbus && !ci_otg_is_fsm_mode(ci) &&
 			(ci->platdata->flags & CI_HDRC_TURN_VBUS_EARLY_ON))