sched/core: Silence a warning in sched_init()

Compiling a kernel with both FAIR_GROUP_SCHED=n and RT_GROUP_SCHED=n
will generate a compiler warning:

  kernel/sched/core.c: In function 'sched_init':
  kernel/sched/core.c:5906:32: warning: variable 'ptr' set but not used

It is unnecessary to have both "alloc_size" and "ptr", so just combine
them.
Signed-off-by: Qian Cai <cai@lca.pw>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: valentin.schneider@arm.com
Link: https://lkml.kernel.org/r/20190720012319.884-1-cai@lca.pwSigned-off-by: Ingo Molnar <mingo@kernel.org>

kernel/sched/core.c

@@ -6430,19 +6430,19 @@ DECLARE_PER_CPU(cpumask_var_t, select_idle_mask);
 
 void __init sched_init(void)
 {
-	unsigned long alloc_size = 0, ptr;
+	unsigned long ptr = 0;
 	int i;
 
 	wait_bit_init();
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
-	alloc_size += 2 * nr_cpu_ids * sizeof(void **);
+	ptr += 2 * nr_cpu_ids * sizeof(void **);
 #endif
 #ifdef CONFIG_RT_GROUP_SCHED
-	alloc_size += 2 * nr_cpu_ids * sizeof(void **);
+	ptr += 2 * nr_cpu_ids * sizeof(void **);
 #endif
-	if (alloc_size) {
-		ptr = (unsigned long)kzalloc(alloc_size, GFP_NOWAIT);
+	if (ptr) {
+		ptr = (unsigned long)kzalloc(ptr, GFP_NOWAIT);
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 		root_task_group.se = (struct sched_entity **)ptr;