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>

Documentation/devicetree/bindings/firmware/qcom,scm.txt

+QCOM Secure Channel Manager (SCM)
+
+Qualcomm processors include an interface to communicate to the secure firmware.
+This interface allows for clients to request different types of actions.  These
+can include CPU power up/down, HDCP requests, loading of firmware, and other
+assorted actions.
+
+Required properties:
+- compatible: must contain one of the following:
+ * "qcom,scm-apq8064" for APQ8064 platforms
+ * "qcom,scm-msm8660" for MSM8660 platforms
+ * "qcom,scm-msm8690" for MSM8690 platforms
+ * "qcom,scm" for later processors (MSM8916, APQ8084, MSM8974, etc)
+- clocks: One to three clocks may be required based on compatible.
+ * Only core clock required for "qcom,scm-apq8064", "qcom,scm-msm8660", and "qcom,scm-msm8960"
+ * Core, iface, and bus clocks required for "qcom,scm"
+- clock-names: Must contain "core" for the core clock, "iface" for the interface
+  clock and "bus" for the bus clock per the requirements of the compatible.
+
+Example for MSM8916:
+
+	firmware {
+		scm {
+			compatible = "qcom,scm";
+			clocks = <&gcc GCC_CRYPTO_CLK> , <&gcc GCC_CRYPTO_AXI_CLK>, <&gcc GCC_CRYPTO_AHB_CLK>;
+			clock-names = "core", "bus", "iface";
+		};
+	};