s390: switch to generic old sigaction()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/s390/include/asm/signal.h

@@ -21,12 +21,5 @@ typedef struct {
         unsigned long sig[_NSIG_WORDS];
 } sigset_t;
 
-struct old_sigaction {
-        __sighandler_t sa_handler;
-        old_sigset_t sa_mask;
-        unsigned long sa_flags;
-        void (*sa_restorer)(void);
-};
-
 #define __ARCH_HAS_SA_RESTORER
 #endif