USB: typec: tps6598x: Refactor tps6598x port registration

tps6598x and cd321x use TPS_REG_SYSTEM_CONF to get dr/pr roles
where other similar devices don't have this register such as tps25750.

Move tps6598x port registration to its own function

Signed-off-by: Abdel Alkuor <abdelalkuor@geotab.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20231003155842.57313-5-alkuor@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>