i40e: split some code in i40e_reset_vf into helpers

A future patch is going to want to re-use some of the code in
i40e_reset_vf, so lets break up the beginning and ending parts into
their own helper functions. The first function will be used to
initialize the reset on a VF, while the second function will be used to
finalize the reset and restore functionality.

Change-ID: I48df808b8bf09de3c2ed8c521f57b3f0ab9e5907
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>