nfp: avoid newline at end of message in NL_SET_ERR_MSG_MOD

Fix the following coccicheck warning:
./drivers/net/ethernet/netronome/nfp/flower/qos_conf.c:750:7-55: WARNING
avoid newline at end of message in NL_SET_ERR_MSG_MOD

Signed-off-by: Wan Jiabing <wanjiabing@vivo.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/r/20220301112356.1820985-1-wanjiabing@vivo.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>