qlcnic: fix data structure corruption in async mbx command handling

This patch fixes a data structure corruption bug in the SRIOV VF mailbox
handler code. While handling mailbox commands from the atomic context,
driver is accessing and updating qlcnic_async_work_list_struct entry fields
in the async work list. These fields could be concurrently accessed by the
work function resulting in data corruption.

This patch restructures async mbx command handling by using a separate
async command list instead of using a list of work_struct structures.
A single work_struct is used to schedule and handle the async commands
with proper locking mechanism.

Signed-off-by: Rajesh Borundia <rajesh.borundia@qlogic.com>
Signed-off-by: Sony Chacko <sony.chacko@qlogic.com>
Signed-off-by: Manish Chopra <manish.chopra@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>