Fix typos from signal_32/64.h merge

Fallout from commit 33185c50 ("x86:
merge signal_32/64.h")

Thanks to Dick Streefland who provided an useful testcase on
http://lkml.org/lkml/2008/3/17/205

 (only applicable to 2.6.24.x), that
helped a lot as a deterministic way to bisect an issue that leaded to
this fix.

Signed-off-by: Herton Ronaldo Krzesinski <herton@mandriva.com.br>
Signed-off-by: Luiz Fernando N. Capitulino <lcapitulino@mandriva.com.br>
Cc: Roland McGrath <roland@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>