ARC: [axs101] Prepare for AXS103

To avoid duplicating the MB DTS file, move the MB intc entry into cpu
card specific file

Cc: Grant Likely <grant.likely@linaro.org>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: devicetree@vger.kernel.org
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>