arm64: tegra: Add PEX DPD states as pinctrl properties

Add PEX deep power down states as pinctrl properties to set in PCIe driver.
In Tegra210, BIAS pads are not in power down mode when clamps are applied.
To set the pads in DPD, pass the PEX DPD states as pinctrl properties to
PCIe driver.

Signed-off-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>