docs(layerscape): add ls1088a soc and board support

Update document for nxp-layerscape to add ls1088a SoC and ls1088ardb,
update maintainer of ls1088a platforms.

Signed-off-by: Jiafei Pan <Jiafei.Pan@nxp.com>
Change-Id: Ic7fdc7b1bbf22e50646991093366a88ee523ffe3
2 files changed