usb: xhci-tegra: Add OTG support

Get usb-phy's for availbale USB 2 phys. Register id notifiers for available
usb-phy's to receive role change notifications. Perform PP for the received
role change usb ports.

Signed-off-by: Nagarjuna Kristam <nkristam@nvidia.com>
[treding@nvidia.com: rebase onto Greg's usb-next branch]
Signed-off-by: Thierry Reding <treding@nvidia.com>