dt-bindings: thermal: tsens: add msm8956 compat

When adding support for msm8976 it was thought that msm8956 would reuse
the same compat. However checking the vendor kernel revealed that these
two platforms use different slope values for calculating the calibration
data.

Add new compatible for the tsens on msm8956 SoC.

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>