ramips: backport mt7621 PCIs initialization delay patch

ramips: backport mt7621 PCIs initialization delay patch

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Some devices like ZBT WE1326 and ZBT WF3526-P and some Netgear models need
to delay phy port initialization after calling the mt7621_pcie_init_port()
driver function to get into reliable boots for both warm and hard resets.

Signed-off-by: Shiji Yang <yangshiji66@qq.com>