arm64: Fix layerscape mmu setup

With commit 7985cdf7 we converted all systems except for the Layerscape
SoCs to the generic descriptor table based page table setup.

On the Layerscape SoCs however, we just provide an empty table stub
and do the setup ourselves. To reserve enough memory for the tables,
we need to override the default counting mechanism which would end up
with an empty table because we have no maps.

Fixes: 7985cdf7
Reported-by: York Sun <york.sun@nxp.com>
CC: Alison Wang <alison.wang@nxp.com>
CC: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
Tested-by: York Sun <york.sun@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>