net: sparx5: Remove unused GLAG handling in PGID

Removes PGID handling for GLAG since it is not used
yet. According to feedback on previous patch.
https://lore.kernel.org/netdev/20220322081823.wqbx7vud4q7qtjuq@wse-c0155/T/#t

Signed-off-by: Casper Andersson <casper.casan@gmail.com>
Reviewed-by: Steen Hegelund <Steen.Hegelund@microchip.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>