ice: remove switchdev control plane VSI

For slow-path Rx and Tx PF VSI is used. There is no need to have control
plane VSI. Remove all code related to it.

Eswitch rebuild can't fail without rebuilding control plane VSI. Return
void from ice_eswitch_rebuild().

Reviewed-by: Marcin Szycik <marcin.szycik@linux.intel.com>
Signed-off-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Tested-by: Sujai Buvaneswaran <sujai.buvaneswaran@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>