arm64: tegra: Disable XUSB support on Jetson TX2

The recently introduced XUSB support for Jetson TX2 is causing boot, CPU
hotplug and suspend/resume failures according to several reports.

Temporarily work around this by disabling the XUSB controller and XUSB
pad controller nodes in device tree, while we figure out what's causing
this.

Reported-by: Bitan Biswas <bbiswas@nvidia.com>
Reported-by: Jonathan Hunter <jonathanh@nvidia.com>
Tested-by: Bitan Biswas <bbiswas@nvidia.com>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>