[BNX2]: Fix link change handling

Fix some link-related problems by doing a coalesce_now after link
change interrupt to flush out the transient link status.

To facilitate this, the host coalesce cmd register value is cached in
the device structure.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>