PCI: mediatek-gen3: Clean up mtk_pcie_parse_port() with dev_err_probe()

PCI: mediatek-gen3: Clean up mtk_pcie_parse_port() with dev_err_probe()

mtk_pcie_parse_port() in the pcie-mediatek-gen driver has a bunch of

  if (err) {
    dev_err(dev, "error message\n");
    return err; # or goto
  }

patterns.

Simplify these with dev_err_probe(). The system also gains proper deferred
probe messages that can be seen in:

  /sys/kernel/debug/devices_deferred

Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Reviewed-by: Manivannan Sadhasivam <mani@kernel.org>
Link: https://patch.msgid.link/20260324052002.4072430-2-wenst@chromium.org