ixgbevf: Fix code for handling timeout

The VF driver was not designed to correctly handle a message timeout.  As
a result it is possible for one bad message to invalidate all messages
following it until the part is reset.  Instead we should copy the example
in igbvf of how to handle a mailbox event and message timeout.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>