sched, arch: Create asm/preempt.h

In order to prepare to per-arch implementations of preempt_count move
the required bits into an asm-generic header and use this for all
archs.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-h5j0c1r3e3fk015m30h8f1zx@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/avr32/include/asm/Kbuild

@@ -3,3 +3,4 @@ generic-y	+= clkdev.h
 generic-y	+= exec.h
 generic-y	+= trace_clock.h
 generic-y	+= param.h
+generic-y += preempt.h