PCI: apple: Set only available ports up

Iterating over disabled ports results in of_irq_parse_raw() parsing
the wrong "interrupt-map" entries, as it takes the status of the node
into account.

This became apparent after disabling unused PCIe ports in the Apple
Silicon device trees instead of deleting them.

Switching from for_each_child_of_node_scoped() to
for_each_available_child_of_node_scoped() solves this issue.

Fixes: 1e33888f ("PCI: apple: Add initial hardware bring-up")
Fixes: a0189fdf ("arm64: dts: apple: t8103: Disable unused PCIe ports")
Signed-off-by: Janne Grunau <j@jannau.net>
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Tested-by: Janne Grunau <j@jannau.net>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Acked-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/asahi/20230214-apple_dts_pcie_disable_unused-v1-0-5ea0d3ddcde3@jannau.net/
Link: https://lore.kernel.org/asahi/1ea2107a-bb86-8c22-0bbc-82c453ab08ce@linaro.org/
Link: https://patch.msgid.link/20250401091713.2765724-2-maz@kernel.org