Revert "PCI: ecam: Allow cfg->priv to be pre-populated from the root port device"

Revert "PCI: ecam: Allow cfg->priv to be pre-populated from the root port device"

This reverts commit 4900454b4f819e88e9c57ed93542bf9325d7e161.

Now that nobody relies of cfg->priv containing anything useful before the
.init() callback is used, restore the previous behaviour.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://patch.msgid.link/20250625111806.4153773-4-maz@kernel.org