arm64: freescale/imx8mp-evk.dts: reorder nodes alphabetically

The nodes after the root nodes are supposed to be ordered
alphabetically. There is however an expection for &pinctrl that some
consider to be good placed at the end of the file. So only move flexcan1
and flexcan2 to their proper place.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>