mlxsw: spectrum: remove redundant check if err is zero

There is an earlier check and return if err is non-zero, so
the check to see if it is zero is redundant in every iteration
of the loop and hence the check can be removed.

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