PCI: imx6: Enable i.MX6QP PCIe power management support

i.MX6QP PCIe supports the reset logic, thus it can reset itself to the
initialized state when exit from L2 or L3 states.

Enable the i.MX6QP PCIe suspend/resume operations support.

Link: https://lore.kernel.org/r/1645425237-4071-2-git-send-email-hongxing.zhu@nxp.com


Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>