phy: tegra: xusb: Skip single function lane programming

Tegra186 USB2 pads and USB3 pads do not have hardware mux for changing
the pad function. For such "lanes", we can skip the lane mux register
programming.

Signed-off-by: JC Kuo <jckuo@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>