net: dsa: mt7530: fix tristate and help description

Fix description for tristate and help sections which include inaccurate
information.

Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Link: https://lore.kernel.org/r/20230126190110.9124-1-arinc.unal@arinc9.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>