PCI: mediatek-gen3: Move mtk_pcie_setup_irq() out of mtk_pcie_setup()

PCI: mediatek-gen3: Move mtk_pcie_setup_irq() out of mtk_pcie_setup()

mtk_pcie_setup_irq() sets up the IRQ domains for PCI INTx and MSI, and
chains them to the controller's interrupt. It doesn't touch the PCIe
controller itself.

Move mtk_pcie_setup_irq() out of mtk_pcie_setup(), do it earlier so there's
nothing to clean up if it fails, and add an error message if it does fail.
Reorder mtk_pcie_irq_teardown() in the remove callback to follow. Also
create an error path in the probe function.

Suggested-by: Bjorn Helgaas <helgaas@kernel.org>
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
[bhelgaas: commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Link: https://patch.msgid.link/20260324052002.4072430-3-wenst@chromium.org