libpayload: Free usb host controller instance after shutdown

All shutdown() implementations but ehci_shutdown() free the hci_t
structure. This seems correct and the reference to the hci_t shouldn't
be used after shutdown(), so do it in ehci_shutdown(), too.

Change-Id: Ie3506d769e73007735f3211710734a5f0107e43a
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: http://review.coreboot.org/1849
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

payloads/libpayload/drivers/usb/ehci.c

@@ -101,6 +101,9 @@ static void ehci_shutdown (hci_t *controller)
 	free(EHCI_INST(controller)->dummy_qh);
 
 	EHCI_INST(controller)->operation->configflag = 0;
+
+	free(EHCI_INST(controller));
+	free(controller);
 }
 
 enum { EHCI_OUT=0, EHCI_IN=1, EHCI_SETUP=2 };