arm64: tegra: Add PCIe slot supply information in p2972-0000 platform

Add 3.3V and 12V supplies regulators information of x16 PCIe slot in
p2972-0000 platform which is owned by C5 controller and also enable C5
controller.

Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Andrew Murray <andrew.murray@arm.com>