PCI: sky1: Add PCIe host support for CIX Sky1

PCI: sky1: Add PCIe host support for CIX Sky1

Add driver for the CIX Sky1 SoC PCIe Gen4 16 GT/s controller based on the
Cadence High Performance Architecture (HPA) PCIe core.

The controller supports MSI/MSI-X via GICv3, Single Virtual Channel, and
Single Function.

Signed-off-by: Hans Zhang <hans.zhang@cixtech.com>
[mani: moved the PCI ID definitions and squashed Kconfig change]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
[bhelgaas: sort Kconfig menu entry, squash
https://lore.kernel.org/r/aSBqp0cglr-Sc8na@stanley.mountain]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20251108140305.1120117-8-hans.zhang@cixtech.com