dt-bindings: introduce RPMH RSC bindings for Qualcomm SoCs

Add device binding documentation for Qualcomm Technology Inc's RPMH RSC
driver. The driver is used for communicating resource state requests for
shared resources.

Cc: devicetree@vger.kernel.org
Signed-off-by: Lina Iyer <ilina@codeaurora.org>
Reviewed-by: Rob Herring <robh@kernel.org>
[rplsssn@codeaurora.org: minor order correction for TCS type]
Signed-off-by: Raju P.L.S.S.S.N <rplsssn@codeaurora.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>