arm64: dts: imx8mm: Add dbi2 and atu reg for i.MX8MM PCIe EP

arm64: dts: imx8mm: Add dbi2 and atu reg for i.MX8MM PCIe EP

Add dbi2 and iatu reg for i.MX8MM PCIe EP.

For i.MX8M PCIe EP, the dbi2 and atu addresses are pre-defined in the
driver. This method is not good.

In commit b7d67c6130ee ("PCI: imx6: Add iMX95 Endpoint (EP) support"),
Frank suggests to fetch the dbi2 and atu from DT directly. This commit is
preparation to do that for i.MX8MM PCIe EP.

These changes wouldn't break driver function. When "dbi2" and "atu"
properties are present, i.MX PCIe driver would fetch the according base
addresses from DT directly. If only two reg properties are provided, i.MX
PCIe driver would fall back to the old method.

Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>