ixgbevf: Add bit to mark work queue initialization

An indication of work queue initialization is needed. This is
because register accesses prior to that time can detect a removal
and attempt to schedule the watchdog task. Adding the
__IXGBEVF_WORK_INIT bit allows this to be checked and if not
set prevent the watchdog task scheduling. By checking for a
removal right after initialization, the probe can be failed
at that point without getting the watchdog task involved.

Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>