sched/core: Make sched_dynamic_mutex static

The sched_dynamic_mutex is only used within the file.  Make it static.

Fixes: e3ff7c6 ("livepatch,sched: Add livepatch task switching to cond_resched()")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/oe-kbuild-all/202304062335.tNuUjgsl-lkp@intel.com/

Author: jpoimboe

kernel/sched/core.c

@@ -8674,7 +8674,7 @@ int sched_dynamic_mode(const char *str)
 #error "Unsupported PREEMPT_DYNAMIC mechanism"
 #endif
 
-DEFINE_MUTEX(sched_dynamic_mutex);
+static DEFINE_MUTEX(sched_dynamic_mutex);
 static bool klp_override;
 
 static void __sched_dynamic_update(int mode)