arm64: dts: imx8mm: Deduplicate PCIe clock-names property

Move the PCIe clock-names property from various DTs into SoC dtsi to
reduce duplication. In case of a couple of boards, reorder the clock
so they match the order in yaml DT bindings.

Reviewed-by: Alexander Stein <alexander.stein@ew.tq-group.com> # imx8mm.dtsi, imx8mm-tqma8mqml-mba8mx.dts
Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Richard Zhu <hongxing.zhu@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>