i40e: fix handling of HW ATR eviction

A recent commit to refactor the driver and remove the hw_disabled_flags
field accidentally introduced two regressions. First, we overwrote
pf->flags which removed various key flags including the MSI-X settings.

Additionally, it was intended that we have now two flags,
HW_ATR_EVICT_CAPABLE and HW_ATR_EVICT_ENABLED, but this was not done,
and we accidentally were mis-using HW_ATR_EVICT_CAPABLE everywhere.

This patch adds the missing piece, HW_ATR_EVICT_ENABLED, and safely
updates pf->flags instead of overwriting it.

Without this patch we will have many problems including disabling MSI-X
support, and we'll attempt to use HW ATR eviction on devices which do
not support it.

Fixes: 47994c11 ("i40e: remove hw_disabled_flags in favor of using separate flag bits", 2017-04-19)
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>