net/mlxfw: remove redundant goto on error check

The check to see of err is set and the subsequent goto is extraneous
as the next statement is where the goto is jumping to. Remove this
redundant check and goto.

Detected by CoverityScan, CID#1437734 ("Identical code for
different branches")

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Yotam Gigi <yotamg@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>