net: fec: add pm_qos support on imx6q platform

There is a very low probability that tx timeout will occur during
suspend and resume stress test on imx6q platform. So we add pm_qos
support to prevent system from entering low level idles which may
affect the transmission of tx.

Signed-off-by: Wei Fang <wei.fang@nxp.com>
Link: https://lore.kernel.org/r/20220830070148.2021947-1-wei.fang@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>