qlge: Add worker-handler for firmware events.

This worker and it's supporting routines are used for
IDC 'inter-device-communication' events that require
an ACK mailbox command be sent to allow completion
of the request. These requests are originated by
another function wanting to change some common
port paramters. Typical example would be:

1) Change max TX/RX frame size allowed.
2) Change pause parameters.
3) Change loopback mode.

Signed-off-by: Ron Mercer <ron.mercer@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>