PCI: mediatek-gen3: Disable device if further setup fails

PCI: mediatek-gen3: Disable device if further setup fails

If further setup fails after the device is powered on and link training
succeeds, we want to place the device back in a quiescence state to avoid
unintended activity and save power. This also helps with power state
tracking and balancing once pwrctrl API is integrated.

Power down the device in the error paths of mtk_pcie_startup_port() and
mtk_pcie_probe().

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/20260324052002.4072430-7-wenst@chromium.org