arm64: dts: imx8mm: Add the pcie support

arm64: dts: imx8mm: Add the pcie support

Add the PCIe support on i.MX8MM platforms.

Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
Tested-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Reviewed-by: Tim Harvey <tharvey@gateworks.com>
Tested-by: Tim Harvey <tharvey@gateworks.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>
Signed-off-by: Marek Vasut <marex@denx.de> # Pick from Linux 854a4766ac12 ("arm64: dts: imx8mm: Add the pcie support")