Fixed -Wnon-virtual-dtor warnings

Signed-off-by: Jerin Joy <joy@rivosinc.com>

fesvr/memif.h

@@ -33,6 +33,8 @@ public:
   virtual memif_endianness_t get_target_endianness() const {
     return memif_endianness_undecided;
   }
+
+  virtual ~chunked_memif_t() = default;
 };
 
 class memif_t

riscv/simif.h

@@ -19,6 +19,8 @@ public:
 
   virtual const char* get_symbol(uint64_t addr) = 0;
 
+  virtual ~simif_t() = default;
+
 };
 
 #endif

riscv/trap.h

@@ -33,6 +33,8 @@ class trap_t
     return _name;
   }
 
+  virtual ~trap_t() = default;
+
  private:
   char _name[16];
   reg_t which;