nfp: abm: fix a memory leak bug

In function nfp_abm_vnic_set_mac, pointer nsp is allocated by nfp_nsp_open.
But when nfp_nsp_has_hwinfo_lookup fail, the pointer is not released,
which can lead to a memory leak bug. Fix this issue by adding
nfp_nsp_close(nsp) in the error path.

Fixes: f6e71efd

 ("nfp: abm: look up MAC addresses via management FW")
Signed-off-by: Qiushi Wu <wu000273@umn.edu>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>