sched, x86: Optimize the preempt_schedule() call

Remove the bloat of the C calling convention out of the
preempt_enable() sites by creating an ASM wrapper which allows us to
do an asm("call ___preempt_schedule") instead.

calling.h bits by Andi Kleen

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-tk7xdi1cvvxewixzke8t8le1@git.kernel.org
[ Fixed build error. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --cc arch/x86/include/asm/calling.h
Simple merge

diff --cc arch/x86/include/asm/preempt.h
Simple merge

diff --cc arch/x86/kernel/Makefile
Simple merge

diff --cc arch/x86/kernel/i386_ksyms_32.c
Simple merge

diff --cc arch/x86/kernel/preempt.S
Simple merge

diff --cc arch/x86/kernel/x8664_ksyms_64.c
Simple merge

diff --cc include/asm-generic/preempt.h
Simple merge

diff --cc include/linux/preempt.h
Simple merge