sched: Use proper type in sched_getaffinity()

Using the proper type fixes the following compiler warning:

  kernel/sched.c:4850: warning: comparison of distinct pointer types lacks a cast
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: torvalds@linux-foundation.org
Cc: travis@sgi.com
Cc: peterz@infradead.org
Cc: drepper@redhat.com
Cc: rja@sgi.com
Cc: sharyath@in.ibm.com
Cc: steiner@sgi.com
LKML-Reference: <20100317090046.4C79.A69D9226@jp.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/sched.c

@@ -4912,7 +4912,7 @@ SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len,
 
 	ret = sched_getaffinity(pid, mask);
 	if (ret == 0) {
-		int retlen = min(len, cpumask_size());
+		size_t retlen = min_t(size_t, len, cpumask_size());
 
 		if (copy_to_user(user_mask_ptr, mask, retlen))
 			ret = -EFAULT;