dt/bindings: firmware: Add Qualcomm SCM binding

This patch adds the device tree support for the Qualcomm SCM firmware.

Signed-off-by: Andy Gross <andy.gross@linaro.org>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Acked-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>