nfp: fix error return code in nfp_pci_probe()

Fix to return error code -EINVAL instead of 0 when num_vfs above
limit_vfs, as done elsewhere in this function.

Fixes: 0dc78621

 ("nfp: handle SR-IOV already enabled when driver is probing")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>