net: dsa: mt7530: remove now incorrect comment regarding port 5

[ Upstream commit feb03fd1 ]

Remove now incorrect comment regarding port 5 as GMAC5. This is supposed to
be supported since commit 38f790a8 ("net: dsa: mt7530: Add support for
port 5") under mt7530_setup_port5().

Fixes: 38f790a8

 ("net: dsa: mt7530: Add support for port 5")
Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Link: https://lore.kernel.org/r/20230310073338.5836-1-arinc.unal@arinc9.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>