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>