dt: bindings: add bindings for msa memory region

Add device tree binding documentation details of msa
memory region for ath10k qmi client for SDM845/APQ8098
SoC into "qcom,ath10k.txt".

Signed-off-by: Govind Singh <govinds@codeaurora.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Acked-by: Niklas Cassel <niklas.cassel@linaro.org>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>