usb: host: tegra: make use of PHY pointer of HCD

As pointer to PHY structure can be stored in struct usb_hcd
making use of it, to call Tegra PHY APIs.

Call to usb_phy_shutdown() is moved up in tegra_ehci_remove(),
so that to avoid dereferencing of hcd after its freed up.

Signed-off-by: Venu Byravarasu <vbyravarasu@nvidia.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Felipe Balbi <balbi@ti.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stephen Warren <swarren@nvidia.com>