sched/headers: Prepare header dependency changes, move the <asm/paravirt.h> include to kernel/sched/sched.h

Recent header reorganizations unearthed this hidden dependency:

  kernel/sched/core.c:199:25: error: 'paravirt_steal_rq_enabled' undeclared (first use in this function)
  kernel/sched/core.c:200:11: error: implicit declaration of function 'paravirt_steal_clock' [-Werror=implicit-function-declaration]

So move the asm/paravirt.h include from kernel/sched/cpuclock.c to kernel/sched/sched.h.

( NOTE: We do this change before doing the changes that introduce the build failure,
        so the series remains fully bisectable. )

Reported-by: kbuild test robot <fengguang.wu@intel.com>
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>

kernel/sched/cputime.c

@@ -6,10 +6,6 @@
 #include <linux/context_tracking.h>
 #include <linux/cputime.h>
 #include "sched.h"
-#ifdef CONFIG_PARAVIRT
-#include <asm/paravirt.h>
-#endif
-
 
 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
 

kernel/sched/sched.h

@@ -20,6 +20,10 @@
 #include <linux/tick.h>
 #include <linux/slab.h>
 
+#ifdef CONFIG_PARAVIRT
+#include <asm/paravirt.h>
+#endif
+
 #include "cpupri.h"
 #include "cpudeadline.h"
 #include "cpuacct.h"