block/rnbd-clt: Use put_cpu_ptr after get_cpu_ptr

This patch replaces put_cpu_var with put_cpu_ptr because
get_cpu_ptr should be paired with put_cpu_ptr.

Signed-off-by: Gioh Kim <gi-oh.kim@ionos.com>
Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
Link: https://lore.kernel.org/r/20210726115950.470543-2-jinpu.wang@ionos.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>