PCI: tegra194: Extend Endpoint mode support

Since only Controller-5 can be used in the Endpoint mode in P2972-0000
platform, support is available only for Controller-5.

Extend that support by enabling the Endpoint mode capable controller during
initialization which otherwise is not required if it is only Controller-5.

Link: https://lore.kernel.org/r/20220721142052.25971-16-vidyas@nvidia.com


Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>