arm64: dts: imx8mp: Reorder clock to match fsl,imx6q-pcie.yaml

Reorder the PCIe clock in DT to match YAML DT schema. No functional change.

Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Richard Zhu <hongxing.zhu@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>