consolidate kernel-side struct sigaction declarations

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/arch/powerpc/include/asm/signal.h b/arch/powerpc/include/asm/signal.h
index a101637..fbe66c4 100644
--- a/arch/powerpc/include/asm/signal.h
+++ b/arch/powerpc/include/asm/signal.h
@@ -1,6 +1,7 @@
 #ifndef _ASM_POWERPC_SIGNAL_H
 #define _ASM_POWERPC_SIGNAL_H
 
+#define __ARCH_HAS_SA_RESTORER
 #include <uapi/asm/signal.h>
 
 #endif /* _ASM_POWERPC_SIGNAL_H */
diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
index 5c51659..2193653 100644
--- a/arch/powerpc/include/asm/syscalls.h
+++ b/arch/powerpc/include/asm/syscalls.h
@@ -9,7 +9,6 @@
 
 struct pt_regs;
 struct rtas_args;
-struct sigaction;
 
 asmlinkage unsigned long sys_mmap(unsigned long addr, size_t len,
 		unsigned long prot, unsigned long flags,