sched/topology: Move sd_flag_debug out of #ifdef CONFIG_SYSCTL

The last sd_flag_debug shuffle inadvertently moved its definition within
an #ifdef CONFIG_SYSCTL region. While CONFIG_SYSCTL is indeed required to
produce the sched domain ctl interface (which uses sd_flag_debug to output
flag names), it isn't required to run any assertion on the sched_domain
hierarchy itself.

Move the definition of sd_flag_debug to a CONFIG_SCHED_DEBUG region of
topology.c.

Now at long last we have:

- sd_flag_debug declared in include/linux/sched/topology.h iff
  CONFIG_SCHED_DEBUG=y
- sd_flag_debug defined in kernel/sched/topology.c, conditioned by:
  - CONFIG_SCHED_DEBUG, with an explicit #ifdef block
  - CONFIG_SMP, as a requirement to compile topology.c

With this change, all symbols pertaining to SD flag metadata (with the
exception of __SD_FLAG_CNT) are now defined exclusively within topology.c

Fixes: 8fca9494 ("sched/topology: Move sd_flag_debug out of linux/sched/topology.h")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200908184956.23369-1-valentin.schneider@arm.com

kernel/sched/debug.c

@@ -245,12 +245,6 @@ set_table_entry(struct ctl_table *entry,
 	entry->proc_handler = proc_handler;
 }
 
-#define SD_FLAG(_name, mflags) [__##_name] = { .meta_flags = mflags, .name = #_name },
-const struct sd_flag_debug sd_flag_debug[] = {
-#include <linux/sched/sd_flags.h>
-};
-#undef SD_FLAG
-
 static int sd_ctl_doflags(struct ctl_table *table, int write,
 			  void *buffer, size_t *lenp, loff_t *ppos)
 {

kernel/sched/topology.c

@@ -25,6 +25,12 @@ static inline bool sched_debug(void)
 	return sched_debug_enabled;
 }
 
+#define SD_FLAG(_name, mflags) [__##_name] = { .meta_flags = mflags, .name = #_name },
+const struct sd_flag_debug sd_flag_debug[] = {
+#include <linux/sched/sd_flags.h>
+};
+#undef SD_FLAG
+
 static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level,
 				  struct cpumask *groupmask)
 {