merging perf counters

hw/rtl/interfaces/VX_perf_cache_if.v

@@ -0,0 +1,20 @@
+`ifndef VX_PERF_CACHE_IF
+`define VX_PERF_CACHE_IF
+
+`include "VX_define.vh"
+
+interface VX_perf_cache_if ();
+
+    wire [63:0] reads;
+    wire [63:0] writes;    
+    wire [63:0] read_misses;
+    wire [63:0] write_misses;
+    wire [63:0] evictions;
+    wire [63:0] mshr_stalls;
+    wire [63:0] crsp_stalls;
+    wire [63:0] dreq_stalls;
+    wire [63:0] pipe_stalls;    
+
+endinterface
+
+`endif