board/fsl/layerscape: Modify the aliases names

when compiling dts file using DTC_FLAG='-@', the device tree compiler
reports these warnings:

Warning (alias_paths): /aliases: aliases property name must include
only lowercase and '-'

Fixed the node aliases to silence these warnings.

Signed-off-by: Pankaj Bansal <pankaj.bansal@nxp.com>
Reviewed-by: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>