be2net: make SET_LOOPBACK_MODE cmd asynchrounous

The SET_LOOPBACK_MODE command is always issued from ethtool only in a
process context. So, while waiting for the cmd to complete, the driver
can sleep instead of holding spin_lock_bh() on the mcc_lock. This is done
by calling be_mcc_notify() instead of be_mcc_notify_wait() (that returns
only after the cmd completes while the MCCQ is locked).

Signed-off-by: Suresh Reddy <suresh.reddy@avagotech.com>
Signed-off-by: Sathya Perla <sathya.perla@avagotech.com>
Signed-off-by: David S. Miller <davem@davemloft.net>