fix invalid usage of mcontext_t in powerpc signal.h
diff --git a/arch/powerpc/bits/signal.h b/arch/powerpc/bits/signal.h
index d633694..c304450 100644
--- a/arch/powerpc/bits/signal.h
+++ b/arch/powerpc/bits/signal.h
@@ -27,7 +27,7 @@
 	struct __ucontext *uc_link;
 	stack_t uc_stack;
 	int uc_pad[7];
-	struct mcontext_t *uc_regs;
+	mcontext_t *uc_regs;
 	
 	sigset_t uc_sigmask;