Compliance test suite: Prefer D over I accesses

Give higher priority to data accesses from the CPU to improve
performance. This is the recommended setup for Ibex.
The test utility host needs still higher priority, otherwise the CPU
takes all bus capacity (the downside of strict priority arbitration).

dv/riscv_compliance/rtl/ibex_riscv_compliance.sv

@@ -23,10 +23,11 @@ module ibex_riscv_compliance (
   assign clk_sys = IO_CLK;
   assign rst_sys_n = IO_RST_N;
 
+  // Bus hosts, ordered in decreasing priority
   typedef enum {
     TestUtilHost,
-    CoreI,
-    CoreD
+    CoreD,
+    CoreI
   } bus_host_e;
 
   typedef enum {