net: ethernet: mtk_eth_soc: avoid writing to ESW registers on MT7628

net: ethernet: mtk_eth_soc: avoid writing to ESW registers on MT7628

The MT7628 has a fixed-link PHY and does not expose MAC control
registers. Writes to these registers only corrupt the ESW VLAN
configuration.

This patch explicitly registers no-op phylink_mac_ops for MT7628, as
after removing the invalid register accesses, the existing
phylink_mac_ops effectively become no-ops.

This code was introduced by commit 296c9120752b
("net: ethernet: mediatek: Add MT7628/88 SoC support")

Signed-off-by: Joris Vaisvila <joey@tinyisr.com>
Reviewed-by: Daniel Golle <daniel@makrotpia.org>
Reviewed-by: Stefan Roese <stefan.roese@mailbox.org>
Link: https://patch.msgid.link/20260226154547.68553-1-joey@tinyisr.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>