dt-bindings: mfd: qcom,tcsr: Add compatible for MSM8976

Document the qcom,msm8976-tcsr compatible.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20221104172122.252761-7-angelogioacchino.delregno@collabora.com