qlcnic: Take FW dump via ethtool

Driver checks if the previous dump has been cleared before taking the dump.
It doesn't take the dump if it is not cleared.

Changes from v2:
Added lock to protect dump data structures from being mangled while
dumping or setting them via ethtool.

Signed-off-by: Anirban Chakraborty <anirban.chakraborty@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>