i40e: fix inconsistent statuses after a PF reset

This patch fixes a problem of possibly getting inconsistent flow control
statuses after a PF reset. Requested_mode was being set with a default
value during probing, but the initial HW state could be different from
this mode.

Change-ID: I772bf07b78616e87086418d4bd87954b66fa17cd
Signed-off-by: Helin Zhang <helin.zhang@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>