USB: EHCI: tegra: Fix use-after-free in .remove()

The tegra_ehci_hcd structure is located in the private space allocated
by the core USB code so it must not be accessed after the HCD is
freed.

Signed-off-by: Tuomas Tynkkynen <ttynkkynen@nvidia.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>