PCI: qcom: Add support for Qualcomm SA8255p based PCIe Root Complex

PCI: qcom: Add support for Qualcomm SA8255p based PCIe Root Complex

Add functionality to enable resource management (like clocks, regulators,
PHY) through firmware and enumerate ECAM compliant Root Complex on SA8255p
SoC, where the PCIe Root Complex is firmware managed and configured into
ECAM compliant mode.

Signed-off-by: Mayank Rana <mayank.rana@oss.qualcomm.com>
[mani: minor code cleanups and commit message rewording]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
[bhelgaas: add "ECAM" in comment]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20250616224259.3549811-5-mayank.rana@oss.qualcomm.com