qlcnic: Remove holding api lock while taking the dump

With the change in logic for taking FW dump across multiple drivers,
there is no need to hold onto the api lock anymore in the fw dump path.
Instead use rtnl_lock() to synchronize the access to FW dump data structs.

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