be_set_phys_id() returns 0 to ethtool when the command fails in the FW.

This patch fixes the set_phys_id() to return -EIO in case the FW cmd fails.
Signed-off-by: Suresh Reddy <suresh.reddy@broadcom.com>
Signed-off-by: Sriharsha Basavapatna <sriharsha.basavapatna@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>