padata: replace cpumask_weight with cpumask_empty in padata.c

padata_do_parallel() calls cpumask_weight() to check if any bit of a
given cpumask is set. We can do it more efficiently with cpumask_empty()
because cpumask_empty() stops traversing the cpumask as soon as it finds
first set bit, while cpumask_weight() counts all bits unconditionally.
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

kernel/padata.c

@@ -181,7 +181,7 @@ int padata_do_parallel(struct padata_shell *ps,
 		goto out;
 
 	if (!cpumask_test_cpu(*cb_cpu, pd->cpumask.cbcpu)) {
-		if (!cpumask_weight(pd->cpumask.cbcpu))
+		if (cpumask_empty(pd->cpumask.cbcpu))
 			goto out;
 
 		/* Select an alternate fallback CPU and notify the caller. */