usb: ehci: fix memory leak in ehci

In usb_ehci_init function, it initializes 's->ipacket', but there
is no corresponding function to free this. As the ehci can be hotplug
and unplug, this will leak host memory leak. In order to make the
hierarchy clean, we should add a ehci pci finalize function, then call
the clean function in ehci device.

Signed-off-by: Li Qiang <liqiang6-s@360.cn>
Message-id: 589a85b8.3c2b9d0a.b8e6.1434@mx.google.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
