s390/ipl: remove non-existing functions declaration

do_reipl, do_halt and do_poff are not defined anywhere. Cleaning up
functions declaration.
Reviewed-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NVasily Gorbik <gor@linux.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/ipl.h

@@ -88,9 +88,6 @@ void __init save_area_add_regs(struct save_area *, void *regs);
 void __init save_area_add_vxrs(struct save_area *, __vector128 *vxrs);
 
 extern void s390_reset_system(void);
-extern void do_reipl(void);
-extern void do_halt(void);
-extern void do_poff(void);
 extern void ipl_store_parameters(void);
 extern size_t append_ipl_vmparm(char *, size_t);
 extern size_t append_ipl_scpdata(char *, size_t);