Explicitly zap some S-mode CSRs when not using S-mode

src/main/scala/rocket/csr.scala

@@ -626,6 +626,16 @@ class CSRFile(implicit p: Parameters) extends CoreModule()(p)
   reg_mip := io.interrupts
   reg_dcsr.debugint := io.interrupts.debug
 
+  if (!usingVM) {
+    reg_mideleg := 0
+    reg_medeleg := 0
+    reg_mscounteren := 0
+  }
+
+  if (!usingUser) {
+    reg_mucounteren := 0
+  }
+
   reg_sptbr.asid := 0
   if (nBreakpoints <= 1) reg_tselect := 0
   if (nBreakpoints >= 1)