sched: Remove never used code in mm_cid_get()

Clang is not happy with set but unused variable (this is visible
with `make W=1` build:

  kernel/sched/sched.h:3744:18: error: variable 'cpumask' set but not used [-Werror,-Wunused-but-set-variable]

It seems like the variable was never used along with the assignment
that does not have side effects as far as I can see.  Remove those
altogether.

Fixes: 223baf9d17f2 ("sched: Fix performance regression introduced by mm_cid")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Eric Biggers <ebiggers@kernel.org>
Reviewed-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 1f5d070..361f910 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -3740,11 +3740,9 @@ static inline int mm_cid_get(struct rq *rq, struct task_struct *t,
 			     struct mm_struct *mm)
 {
 	struct mm_cid __percpu *pcpu_cid = mm->pcpu_cid;
-	struct cpumask *cpumask;
 	int cid;
 
 	lockdep_assert_rq_held(rq);
-	cpumask = mm_cidmask(mm);
 	cid = __this_cpu_read(pcpu_cid->cid);
 	if (mm_cid_is_valid(cid)) {
 		mm_cid_snapshot_time(rq, mm);