iavf: Refactor text of informational message

This message is intended to be informational to indicate a reset is about
to happen, but the use of "warning" in the message text can cause concern
with users.  Reword the message to make it less alarming.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Karen Sornek <karen.sornek@intel.com>
Tested-by: George Kuruvinakunnel <george.kuruvinakunnel@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>