[PATCH] x86-64: Minor patch for compilation warning in x86_64 signal code

If DEBUG_SIG is enbaled in source code, ia32_signal.c compiles with warning
due to wrong format string.  Attached patch fixes that.  It is quite minor
update, since by default DEBUG_SIG is not enabled and can not be turned on
without code modification.

Signed-off-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>