Remove compiler warning

cast between incompatible function types from
‘void (*)(int,  int)’ to ‘void (*)(int)’

src/frontend/signal_handler.c

@@ -104,10 +104,8 @@ ft_sigintr(void)
 
 
 RETSIGTYPE
-sigfloat(int sig, int code)
+sigfloat(int code)
 {
-    NG_IGNORE(sig);
-
     fperror("Error", code);
     rewind(cp_out);
     (void) signal(SIGFPE, (SIGNAL_FUNCTION) sigfloat);

src/frontend/signal_handler.h

@@ -7,7 +7,7 @@
 #define ngspice_SIGNAL_HANDLER_H
 
 RETSIGTYPE ft_sigintr(void);
-RETSIGTYPE sigfloat(int sig, int code);
+RETSIGTYPE sigfloat(int code);
 RETSIGTYPE sigstop(void);
 RETSIGTYPE sigcont(void);
 RETSIGTYPE sigill(void);