Documentation: qpnp-bms: Fix DT bindings for calculate-soc-ms

The device tree bindings documentation state that there is a property
named "qcom,soc-calculate-soc-ms". This is incorrect. It should be
"qcom,calculate-soc-ms".

Fix this in the bindings documentation.

Change-Id: I737b9c60818844e65258d8f4f8b9c90f006a7879
Signed-off-by: Xiaozhe Shi <xiaozhes@codeaurora.org>