Remove verilated vpi code, add missing includes for C++

Vortex rtlsim defines sim_trace_enabled... functions in the Verilated
C++ code for use in dpi_trace, which we don't need.

hw/dpi/float_dpi.cpp

@@ -20,7 +20,7 @@
 #include <rvfloats.h>
 #include <util.h>
 #include "svdpi.h"
-#include "verilated_vpi.h"
+// #include "verilated_vpi.h"
 #include "VX_config.h"
 
 extern "C" {
@@ -337,4 +337,4 @@ void dpi_fmax(bool enable, int dst_fmt, int64_t a, int64_t b, int64_t* result, s
   } else {
     *result = nan_box(rv_fmax_s(check_boxing(a), check_boxing(b), fflags));
   }
-}
+}