dt-bindings: clk: add AOP clock controller bindings

The Always on Processor (AOP) found on Qualcomm Technologies, Inc.
SoCs supports enabling, disabling, and scaling several shared
clocks.  These clocks are controlled using the QMP mailbox
protocol.  Add device bindings for AOP clock controllers.

Change-Id: I1d0b6c0abad702b2bd50fd2078eedc0907b85214

bindings/clock/qcom,aop-qmp.txt

@@ -0,0 +1,17 @@
+Qualcomm Technologies, Inc. Always On Processor Clock controller Binding
+------------------------------------------------------------------------
+
+Required properties :
+- compatible : must be "qcom,aop-qmp-clk"
+- #clock-cells : must contain 1
+- mboxes : list of QMP mailbox phandle and channel identifier tuples.
+- mbox-names: List of identifier strings for each mailbox channel.
+		Must contain "qdss_clk".
+
+Example :
+	clock_qdss: qcom,aopclk {
+		compatible = "qcom,aop-qmp-clk";
+		#clock-cells = <1>;
+		mboxes = <&qmp_aop 0>;
+		mbox-names = "qdss_clk";
+	};