* 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.

include/grub/misc.h

@@ -298,7 +298,7 @@ grub_div_roundup (unsigned int x, unsigned int y)
 }
 
 /* Reboot the machine.  */
-void EXPORT_FUNC (grub_reboot) (void);
+void EXPORT_FUNC (grub_reboot) (void) __attribute__ ((noreturn));
 
 #ifdef GRUB_MACHINE_PCBIOS
 /* Halt the system, using APM if possible. If NO_APM is true, don't