PCI: apple: Move port PHY registers to their own reg items

T602x PCIe cores move these registers around. Instead of hardcoding in
another offset, let's move them into their own reg entries. This matches
what Apple does on macOS device trees too.

Maintains backwards compatibility with old DTs by using the old offsets.

Note that we open code devm_platform_ioremap_resource_byname() to avoid
error messages on older platforms with missing resources in the pcie
node. ("pcie-apple 590000000.pcie: invalid resource (null)" on probe)

Co-developed-by: Janne Grunau <j@jannau.net>
Signed-off-by: Janne Grunau <j@jannau.net>
Signed-off-by: Hector Martin <marcan@marcan.st>
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>
Link: https://patch.msgid.link/20250401091713.2765724-10-maz@kernel.org