signals: Prepare to split out <linux/signal_types.h> from <linux/signal.h>

Introduce dummy header and add dependencies to places that will depend on it.

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/signal.h

@@ -1,9 +1,8 @@
 #ifndef _LINUX_SIGNAL_H
 #define _LINUX_SIGNAL_H
 
-#include <linux/list.h>
 #include <linux/bug.h>
-#include <uapi/linux/signal.h>
+#include <linux/signal_types.h>
 
 struct task_struct;