i40e: Move HW flush

This patch moves the HW flush routine to the end of the reset flow,
after the completion of writing to the device VFLR registers- the
benefit is to avoid problems in the passthrough routines.

Change-ID: Ieb56866f21895e6c1fc514b7328c3df79807a57c
Signed-off-by: Akeem G Abodunrin <akeem.g.abodunrin@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>