i40e: use configured RSS key and lookup table in i40e_vsi_config_rss

i40e: use configured RSS key and lookup table in i40e_vsi_config_rss

A previous refactor added support to store user configuration for VSIs,
so that extra VSIs such as for VMDq can use this information when
configuring. Unfortunately the i40e_vsi_config_rss function was missed
in this refactor, and the values were being ignored. Fix this by
checking for the fields and using those instead of always using the
default values.

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>