mediatek: filogic: gl-mt2500 fix compatibles PHY variants

mediatek: filogic: gl-mt2500 fix compatibles PHY variants

These devices share the same "compatible" in device tree causing some
incompatibilities (sysupgrades, ASU profile identification), assign a
unique "compatible" and "model" to each variant.

Context:
Commit [1] added each variant's dts compatible to the SUPPORTED_DEVICES
field of the other variant to make easy sysupgrades between these
physically indistinguishable devices variants possible.

But there were found three issues which does not allow this:
- the sysupgrade's stricter check still used in some sysupgrade
paths(this check is being replaced(and redundant) with the newer fwtool's
SUPPORTED_DEVICES check using the info in images METADATA), this check
will fail when sysupgrading from a different board_name(compatible dts)
that the image was created for (image profile name).[2]
- ASU needs unique "dts compatible" to identify the devices profile.
- and an ASU's profile identification limitation when several devices from
a common target share SUPPORTED_DEVICES entries.[3]

There is a proposal for these issues but not yet implemented [4][3].

Until these issues are fixed we won't allow "easy" sysupgrades between
these two device variants.

Commit [5] avoided the ASU profile identification limitation but
missed the required two unique dts compatibles in order to make the two
variants fully work, although not allowing easy sysupgrade between them.

[1]: https://github.com/openwrt/openwrt/commit/8d30e07180367cdeb4affd79adead6e1025355c9
[2]: sysupgrade stricter check https://github.com/openwrt/openwrt/issues/20566#issuecomment-3583555482
[3]: ASU proposal https://github.com/openwrt/asu/pull/1533
[4]: allow easy sysupgrade proposal https://github.com/openwrt/openwrt/pull/20947
[5]: https://github.com/openwrt/openwrt/commit/b71f4665cda10c284c9460409ae30fb9b0beecf8
Fixes: b71f466 ("mediatek: filogic: fix supported_devices list for gl-mt2500")
Fixes: 8d30e07 ("mediatek: filogic: fix for new GL.iNet GL-MT2500/GL-MT2500A hardware revision")
Fixes: https://github.com/openwrt/openwrt/issues/20566
Fixes: https://github.com/openwrt/asu/issues/1525
Signed-off-by: Mario Andrés Pérez <mapb_@outlook.com>
Link: https://github.com/openwrt/openwrt/pull/21842
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>