arm64: dts: mediatek: mt7986: Fix watchdog compatible

MT7986's watchdog embeds a reset controller and needs only the
mediatek,mt7986-wdt compatible string as the MT6589 one is there
for watchdogs that don't have any reset controller capability.

Fixes: 50137c15 ("arm64: dts: mediatek: add basic mt7986 support")
Signed-off-by: Allen-KH Cheng <allen-kh.cheng@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Link: https://lore.kernel.org/r/20221108033209.22751-4-allen-kh.cheng@mediatek.com


Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>