Internals: Fix remaining cppcheck errors (#6319)

Fixed the non const-related issue and added suppressions for the const
ones. With that `make cppcheck` should be clean.

src/V3TraceDecl.cpp

@@ -316,6 +316,7 @@ class TraceDeclVisitor final : public VNVisitor {
 
     void removeRedundantPrefixPushPop() {
         for (const auto& pair : m_scopeInitFuncps) {
+            // cppcheck-suppress constVariablePointer
             for (AstCFunc* const funcp : pair.second) {
                 AstNode* prevp = nullptr;
                 AstNode* currp = funcp->stmtsp();