usb: ehci: remember init mode

usb: ehci: remember init mode

When an EHCI device is registered in device mode, the HW isn't actually
initialized at all, and hence isn't left in a running state. Consequently,
when the device is deregistered, ehci_shutdown() will fail, since the HW
bits it expects to see set in response to its shutdown requests will not
be sent, and the message "EHCI failed to shut down host controller." will
be printed.

Fix ehci-hcd.c to remember whether the device was registered in host or
device mode, and only call ehci_shutdown() for host mode registrations.

Signed-off-by: Stephen Warren <swarren@nvidia.com>