net: dsa: hellcreek: refactor hellcreek_port_setup_tc() to use switch/case

The following patch will need to make this function also respond to
TC_QUERY_BASE, so make the processing more structured around the
tc_setup_type.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Kurt Kanzenbach <kurt@linutronix.de>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>