block/rnbd: use %pe to print errors

While printing error, replace %ld by %pe. %pe prints a string
whereas %ld would print an error code.

Signed-off-by: Supriti Singh <supriti.singh@ionos.com>
Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
Signed-off-by: Grzegorz Prajsner <grzegorz.prajsner@ionos.com>
Signed-off-by: Md Haris Iqbal <haris.iqbal@ionos.com>
Link: https://lore.kernel.org/r/20231124213422.113449-3-haris.iqbal@ionos.com


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