dt-bindings: arm-smmu: Add compatible for X1E80100 SoC

Add the SoC specific compatible for X1E80100 implementing arm,mmu-500.

Signed-off-by: Rajendra Nayak <quic_rjendra@quicinc.com>
Co-developed-by: Sibi Sankar <quic_sibis@quicinc.com>
Signed-off-by: Sibi Sankar <quic_sibis@quicinc.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>