ice: move ice_vsi_update_l2tsel to ice_lib.c

A future change is going to need to call ice_vsi_update_l2tsel from a new
context outside of ice_virtchnl.c

Since this function deals with a generic VSI, move it into ice_lib.c to
enable calling it from other places in the ice driver.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Madhu Chittim <madhu.chittim@intel.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>