[POWERPC] Implement logging of unhandled signals

Implement show_unhandled_signals sysctl + support to print when a process
is killed due to unhandled signals just as i386 and x86_64 does.

Default to having it off, unlike x86 that defaults on.

Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c
index c434d6c..a65a44f 100644
--- a/arch/powerpc/kernel/signal.c
+++ b/arch/powerpc/kernel/signal.c
@@ -16,6 +16,12 @@
 
 #include "signal.h"
 
+/* Log an error when sending an unhandled signal to a process. Controlled
+ * through debug.exception-trace sysctl.
+ */
+
+int show_unhandled_signals = 0;
+
 /*
  * Allocate space for the signal frame
  */