sched/deadline: Make the grub_reclaim() function static

Since the grub_reclaim() function can be made static, make it so.

Silences the following GCC warning (W=1):

  kernel/sched/deadline.c:1120:5: warning: no previous prototype for ‘grub_reclaim’ [-Wmissing-prototypes]
Signed-off-by: Mathieu Malaterre <malat@debian.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20180516200902.959-1-malat@debian.orgSigned-off-by: Ingo Molnar <mingo@kernel.org>

kernel/sched/deadline.c

@@ -1117,7 +1117,7 @@ extern bool sched_rt_bandwidth_account(struct rt_rq *rt_rq);
  * should be larger than 2^(64 - 20 - 8), which is more than 64 seconds.
  * So, overflow is not an issue here.
  */
-u64 grub_reclaim(u64 delta, struct rq *rq, struct sched_dl_entity *dl_se)
+static u64 grub_reclaim(u64 delta, struct rq *rq, struct sched_dl_entity *dl_se)
 {
 	u64 u_inact = rq->dl.this_bw - rq->dl.running_bw; /* Utot - Uact */
 	u64 u_act;