Btrfs: fix reada debug code compilation

This fixes the following errors:

  fs/btrfs/reada.c: In function ‘btrfs_reada_wait’:
  fs/btrfs/reada.c:958:42: error: invalid operands to binary < (have ‘atomic_t’ and ‘int’)
  fs/btrfs/reada.c:961:41: error: invalid operands to binary < (have ‘atomic_t’ and ‘int’)

Signed-off-by: Vincent Stehlé <vincent.stehle@laposte.net>
Cc: Chris Mason <chris.mason@fusionio.com>
Cc: linux-btrfs@vger.kernel.org
Reviewed-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

fs/btrfs/reada.c

@@ -955,10 +955,11 @@ int btrfs_reada_wait(void *handle)
 	while (atomic_read(&rc->elems)) {
 		wait_event_timeout(rc->wait, atomic_read(&rc->elems) == 0,
 				   5 * HZ);
-		dump_devs(rc->root->fs_info, rc->elems < 10 ? 1 : 0);
+		dump_devs(rc->root->fs_info,
+			  atomic_read(&rc->elems) < 10 ? 1 : 0);
 	}
 
-	dump_devs(rc->root->fs_info, rc->elems < 10 ? 1 : 0);
+	dump_devs(rc->root->fs_info, atomic_read(&rc->elems) < 10 ? 1 : 0);
 
 	kref_put(&rc->refcnt, reada_control_release);