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>