arm64: tegra: Add support for PCIe endpoint mode in P2972-0000 platform

Add endpoint mode support for PCIe C5 controller in P2972-0000 platform
with information about supplies, PHY, PERST GPIO and GPIO that controls
PCIe reference clock coming from the host system.

Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>