mt76: mt7915: set muru platform type

Set muru platform type by mcu cmd to notify fw to init corresponding
algorithm.

Suggested-by: Money Wang <money.wang@mediatek.com>
Reviewed-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Shayne Chen <shayne.chen@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>