PCI: tegra: Add support to configure sideband pins

Add support to configure sideband signal pins when the information is
present in the respective controller device-tree node.

Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
[bhelgaas: fold in YueHaibing's fix for build error without CONFIG_PINCTRL;
https://lore.kernel.org/r/20190920014807.38288-1-yuehaibing@huawei.com

]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Andrew Murray <andrew.murray@arm.com>
Acked-by: Thierry Reding <treding@nvidia.com>