mlx4_code: Add missing FW status return code

Add ICM_ERROR firmware status code.  In mapping to errnos, -ENFILE
seems closest.

This is in preparation for providing more detailed log info using
mlx4_err() in low-level driver when a non-zero status is returned.

Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>