arm64: dts: imx8m: remove unused "nvmem_macaddr_swap" property for FEC

Remove unused "nvmem_macaddr_swap" property for FEC, there is no info in both
dt-binding and driver, so it's safe to remove it.

Reviewed-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Joakim Zhang <qiangqing.zhang@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>