sunrpc: add missing newline when printing parameter 'pool_mode' by sysfs

When I cat parameter '/sys/module/sunrpc/parameters/pool_mode', it
displays as follows. It is better to add a newline for easy reading.

[root@hulk-202 ~]# cat /sys/module/sunrpc/parameters/pool_mode
global[root@hulk-202 ~]#

Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>