dt-bindings: tsens: qcom: Document MSM8939 compatible

It adds compatible for MSM8939 TSENS device.

Signed-off-by: Konrad Dybcio <konradybcio@gmail.com>
Reviewed-by: Amit Kucheria <amit.kucheria@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Tested-by: Konrad Dybcio <konradybcio@gmail.com> /* on Asus Z00T smartphone */
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200629144926.665-2-shawn.guo@linaro.org