* Xilinx AXI Performance monitor IP

Required properties:
- compatible: "xlnx,axi-perf-monitor"
- interrupts: Should contain APM interrupts.
- interrupt-parent: Must be core interrupt controller.
- reg: Should contain APM registers location and length.
- xlnx,enable-profile: Enables the profile mode.
- xlnx,enable-trace: Enables trace mode.
- xlnx,num-monitor-slots: Maximum number of slots in APM.
- xlnx,enable-event-count: Enable event count.
- xlnx,enable-event-log: Enable event logging.
- xlnx,have-sampled-metric-cnt:Sampled metric counters enabled in APM.
- xlnx,num-of-counters: Number of counters in APM
- xlnx,metric-count-width: Metric Counter width (32/64)
- xlnx,metrics-sample-count-width: Sampled metric counter width
- xlnx,global-count-width: Global Clock counter width
- clocks: Input clock specifier.

Optional properties:
- xlnx,id-filter-32bit: APM is in 32-bit mode

Example:
++++++++

apm: apm@44a00000 {
    compatible = "xlnx,axi-perf-monitor";
    interrupt-parent = <&axi_intc_1>;
    interrupts = <1 2>;
    reg = <0x44a00000 0x1000>;
    clocks = <&clkc 15>;
    xlnx,enable-profile = <0>;
    xlnx,enable-trace = <0>;
    xlnx,num-monitor-slots = <4>;
    xlnx,enable-event-count = <1>;
    xlnx,enable-event-log = <1>;
    xlnx,have-sampled-metric-cnt = <1>;
    xlnx,num-of-counters = <8>;
    xlnx,metric-count-width = <32>;
    xlnx,metrics-sample-count-width = <32>;
    xlnx,global-count-width = <32>;
    xlnx,metric-count-scale = <1>;
    xlnx,id-filter-32bit;
};
