nfp: xsk: avoid newline at the end of message in NL_SET_ERR_MSG_MOD

Fix the following coccicheck warning:
drivers/net/ethernet/netronome/nfp/nfp_net_common.c:3434:8-48: WARNING
avoid newline at end of message in NL_SET_ERR_MSG_MOD

Signed-off-by: Guo Zhengkui <guozhengkui@vivo.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>