* include/grub/misc.h (grub_reboot): Declare as noreturn.

* kern/efi/efi.c (grub_reboot): Don't return, even if reset_system
fails.
(grub_halt): Likewise.
* kern/ieee1275/openfw.c (grub_reboot): Don't return, even if
reset-all fails.
(grub_halt): Don't return, even if all of shut-down, power-off, and
poweroff fail.

kern/ieee1275/openfw.c

@@ -420,6 +420,7 @@ void
 grub_reboot (void)
 {
   grub_ieee1275_interpret ("reset-all", 0);
+  for (;;) ;
 }
 #endif
 
@@ -431,4 +432,5 @@ grub_halt (void)
   grub_ieee1275_interpret ("shut-down", 0);
   grub_ieee1275_interpret ("power-off", 0);
   grub_ieee1275_interpret ("poweroff", 0);
+  for (;;) ;
 }