sim: ppc: mark halt & restart funcs as noreturn

This helps the compiler with optimization and fixes fallthru warnings.

sim/ppc/cpu.h

@@ -100,21 +100,21 @@ INLINE_CPU\
 INLINE_CPU\
 (void) cpu_restart
 (cpu *processor,
- unsigned_word nia);
+ unsigned_word nia) ATTRIBUTE_NORETURN;
 
 INLINE_CPU\
 (void) cpu_halt
 (cpu *processor,
  unsigned_word nia,
  stop_reason reason,
- int signal);
+ int signal) ATTRIBUTE_NORETURN;
 
 EXTERN_CPU\
 (void) cpu_error
 (cpu *processor,
  unsigned_word cia,
  const char *fmt,
- ...) ATTRIBUTE_PRINTF_3;
+ ...) ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF_3;
 
 
 /* The processors local concept of time */

sim/ppc/psim.c

@@ -578,7 +578,7 @@ psim_restart(psim *system,
 }
 
 
-static void
+static ATTRIBUTE_NORETURN void
 cntrl_c_simulation(void *data)
 {
   psim *system = data;

sim/ppc/psim.h

@@ -93,7 +93,7 @@ extern void psim_run
 
 extern void psim_restart
 (psim *system,
- int cpu_nr);
+ int cpu_nr) ATTRIBUTE_NORETURN;
 
 extern void psim_set_halt_and_restart
 (psim *system,
@@ -110,7 +110,7 @@ extern void psim_halt
 (psim *system,
  int cpu_nr,
  stop_reason reason,
- int signal);
+ int signal) ATTRIBUTE_NORETURN;
 
 extern int psim_last_cpu
 (psim *system);