block: cfq_cpd_alloc() should use @gfp

cfq_cpd_alloc() which is the cpd_alloc_fn implementation for cfq was
incorrectly hard coding GFP_KERNEL instead of using the mask specified
through the @gfp parameter.  This currently doesn't cause any actual
issues because all current callers specify GFP_KERNEL.  Fix it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: e4a9bde9 ("blkcg: replace blkcg_policy->cpd_size with ->cpd_alloc/free_fn() methods")
Signed-off-by: Jens Axboe <axboe@fb.com>

block/cfq-iosched.c

@@ -1586,7 +1586,7 @@ static struct blkcg_policy_data *cfq_cpd_alloc(gfp_t gfp)
 {
 	struct cfq_group_data *cgd;
 
-	cgd = kzalloc(sizeof(*cgd), GFP_KERNEL);
+	cgd = kzalloc(sizeof(*cgd), gfp);
 	if (!cgd)
 		return NULL;
 	return &cgd->cpd;