consolidate kernel-side struct sigaction declarations

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/arch/parisc/include/asm/signal.h b/arch/parisc/include/asm/signal.h
index e42e05d..c8e4ec5 100644
--- a/arch/parisc/include/asm/signal.h
+++ b/arch/parisc/include/asm/signal.h
@@ -24,11 +24,13 @@
 	unsigned long sig[_NSIG_WORDS];
 } sigset_t;
 
+#ifndef __KERNEL__
 struct sigaction {
 	__sighandler_t sa_handler;
 	unsigned long sa_flags;
 	sigset_t sa_mask;		/* mask last for extensibility */
 };
+#endif
 
 #include <asm/sigcontext.h>