pci: tegra: actually program REFCLK_CFG* on recent SoCs

On recent SoCs, tegra_pcie_phy_enable() isn't called; but instead
tegra_pcie_enable_controller() calls tegra_xusb_phy_enable(). However,
part of tegra_pcie_phy_enable() needs to happen in all cases. Move that
code to tegra_pcie_port_enable() instead.

For reference, NVIDIA's downstream Linux kernel performs this operation
in tegra_pcie_enable_rp_features(), which is called immediately after
tegra_pcie_port_enable(). Since that function doesn't exist in the U-Boot
driver, we'll just add it to the tail of tegra_pcie_port_enable() instead.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>