The offset of the TSSI flag on the EEPROM of MT7981 devices was wrong.
Set the correct offset instead.

Fixes: 6bad146d ("wifi: mt76: mt7915: add support for MT7981")
Signed-off-by: StanleyYP Wang <StanleyYP.Wang@mediatek.com>
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>