UPSTREAM: PCI: of: Add of_pci_preserve_config() for per-host bridge support

Add of_pci_preserve_config() to look for the "linux,pci-probe-only"
property under a specified node.  If it's not found there, look under
"of_chosen" in addition.

If the caller didn't specify a node, look under "of_chosen".

With a future patch, this will support "linux,pci-probe-only" on a per host
bridge basis based on the presence of the property in the respective PCI
host bridge DT node.

Implement of_pci_check_probe_only() using of_pci_preserve_config().

Link: https://lore.kernel.org/r/20240508174138.3630283-3-vidyas@nvidia.com


Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Change-Id: If0927979f48dc5c12074da8c3f902e37573df959
(cherry picked from commit 407abde9)
Signed-off-by: Jian-Min Liu <jianminl@nvidia.com>