PCI: endpoint: Add auxiliary resource query API

PCI: endpoint: Add auxiliary resource query API

Endpoint controller drivers may integrate auxiliary blocks (e.g. DMA
engines) whose register windows and descriptor memories metadata need to
be exposed to a remote peer. Endpoint function drivers need a generic
way to discover such resources without hard-coding controller-specific
helpers.

Add pci_epc_get_aux_resources_count() / pci_epc_get_aux_resources() and
the corresponding pci_epc_ops callbacks. The count helper returns the
number of available resources, while the get helper fills a
caller-provided array of resources described by type, physical address
and size, plus type-specific metadata.

Suggested-by: Manivannan Sadhasivam <mani@kernel.org>
Suggested-by: Frank Li <Frank.li@nxp.com>
Signed-off-by: Koichiro Den <den@valinux.co.jp>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Link: https://patch.msgid.link/20260414141514.1341429-2-den@valinux.co.jp