usb: host: tegra: fix warning messages in ehci_remove

Existing implementation of tegra_ehci_remove() calls
usb_put_hcd(hcd) first and then iounmap(hcd->regs).

usb_put_hcd() implementation calls hcd_release()
which frees up memory allocated for hcd.

As iounmap is trying to unmap hcd->regs, after hcd
getting freed up, warning messages were observed during
unload of USB.

Hence fixing it.

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