qlcnic: Fix mailbox response handling.

o Fix mailbox response poll time to maximum 5 seconds which
  includes mailbox response time as well as time required for
  processing AEN if any.
o Driver need to read firmware control mailbox register instead
  of host control mailbox register.

Signed-off-by: Jitendra Kalsaria <jitendra.kalsaria@qlogic.com>
Signed-off-by: Rajesh Borundia <rajesh.borundia@qlogic.com>
Signed-off-by: Shahed Shaikh <shahed.shaikh@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>