arm: tegra: tec-ng: Workaround the LP2 hang

Switching to the low-power core currently freezes the system. To
workaround this bug until we can fix it,  we just disable the cluster
control that is responsible for the core switching.

Change-Id: I1785b60e967c0a7b377fc5eeb6fe0ce03bd22f2c
Signed-off-by: Alban Bedel <alban.bedel@avionic-design.de>
Reviewed-on: http://review.adnet.avionic-design.de/383
Reviewed-by: Julian Scheel <julian.scheel@avionic-design.de>