dt-bindings: thermal: mediatek: Fix thermal zone definition for MT8186

Fix a thermal zone name for consistency with the other SoCs:
MFG contains GPU, the latter is more specific and must be used here.

The naming must be fixed "atomically" so compilation does not break.
As a result, the change is made in the dt-bindings and in the LVTS
driver within a single commit, despite the checkpatch warning.

The definition can be safely modified here because it is used only
in the LVTS driver, which is modified accordingly, and has not yet
been included in a released kernel.

Fixes: a2ca2023 ("dt-bindings: thermal: mediatek: Add LVTS thermal controller definition for MT8186")
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Julien Panis <jpanis@baylibre.com>
Link: https://lore.kernel.org/r/20240603-mtk-thermal-mt818x-dtsi-v7-1-8c8e3c7a3643@baylibre.com


Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>