Use correct type for saved signal handler

A user noticed that the sim assigns the result of a call to 'signal'
to a variable like:

  RETSIGTYPE (*prev_sigint) ();

However, it's more correct to use (int) here.

This patch fixes the error.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=32466
Approved-By: Andrew Burgess <aburgess@redhat.com>

sim/common/dv-sockser.c

@@ -175,7 +175,7 @@ dv_sockser_init (SIM_DESC sd)
      ??? Need a central signal management module.  */
 #ifdef SIGPIPE
   {
-    RETSIGTYPE (*orig) ();
+    RETSIGTYPE (*orig) (int);
     orig = signal (SIGPIPE, SIG_IGN);
     /* If a handler is already set up, don't mess with it.  */
     if (orig != SIG_DFL && orig != SIG_IGN)

sim/common/nrun.c

@@ -64,7 +64,7 @@ main (int argc, char **argv)
   enum sim_stop reason;
   int sigrc = 0;
   int single_step = 0;
-  RETSIGTYPE (*prev_sigint) ();
+  RETSIGTYPE (*prev_sigint) (int);
 
   myname = lbasename (argv[0]);
 

sim/ppc/main.c

@@ -289,7 +289,7 @@ main(int argc, char * const *argv)
   psim_stack(simulation, argv, environ);
 
   {
-    RETSIGTYPE (*prev) ();
+    RETSIGTYPE (*prev) (int);
     prev = signal(SIGINT, cntrl_c);
     psim_run(simulation);
     signal(SIGINT, prev);