PCI: ultrarisc: Add UltraRISC DP1000 PCIe Root Complex driver

PCI: ultrarisc: Add UltraRISC DP1000 PCIe Root Complex driver

Add DP1000 SoC PCIe Root Complex driver.

The controller only supports 32-bit aligned configuration space accesses.

Signed-off-by: Xincheng Zhang <zhangxincheng@ultrarisc.com>
Signed-off-by: Jia Wang <wangjia@ultrarisc.com>
[mani: changed to builtin_platform_driver() to prevent irqchip removal]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
[bhelgaas: squash MAINTAINERS update here]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20260427-ultrarisc-pcie-v4-3-98935f6cdfb5@ultrarisc.com