wifi: mt76: connac: fix possible unaligned access in mt76_connac_mcu_add_nested_tlv

Fix possible unaligned pointer in mt76_connac_mcu_add_nested_tlv
routine.

Reported-by: kernel test robot <lkp@intel.com>
Fixes: 25702d9c

 ("mt76: connac: rely on le16_add_cpu in mt76_connac_mcu_add_nested_tlv")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>