preempt: Make PREEMPT_ACTIVE generic

No point in having this bit defined by architecture.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20130917183629.090698799@linutronix.de

arch/alpha/include/asm/thread_info.h

@@ -58,8 +58,6 @@ register struct thread_info *__current_thread_info __asm__("$8");
 #define THREAD_SIZE_ORDER 1
 #define THREAD_SIZE (2*PAGE_SIZE)
 
-#define PREEMPT_ACTIVE		0x40000000
-
 /*
  * Thread information flags:
  * - these are process state flags and used from assembly