arm64: dts: imx8mp-phyboard-pollux: Add flexcan support

Add flexcan1 and flexcan2 support for CAN FD on phyBOARD-Pollux.

Signed-off-by: Teresa Remmet <t.remmet@phytec.de>
Signed-off-by: Cem Tenruh <c.tenruh@phytec.de>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>