Add a new driver for the XUSB pad controller found on NVIDIA Tegra SoCs.
This hardware block used to be exposed as a pin controller, but it turns
out that this isn't a good fit. The new driver and DT binding much more
accurately describe the hardware and are more flexible in supporting new
Acked-by: Kishon Vijay Abraham I <firstname.lastname@example.org>
Signed-off-by: Thierry Reding <email@example.com>