PCI: imx6: Disable i.MX6QDL clock when disabling ref clocks

When disabling PCIe clocks, disable i.MX6QDL ref clock too.

Link: https://lore.kernel.org/r/1657783869-19194-9-git-send-email-hongxing.zhu@nxp.com
Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>