arm64: dts: imx8m: Add the ENET PPS interrupt

The i.MX8M SoCs have a fourth ENET interrupt dedicated to PPS (Pulse Per
Second). Add support for it.

Suggested-by: Rogerio Nunes <rogerio.nunes@nxp.com>
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Fugang Duan <fugang.duan@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>