mt76: mt7615: introduce mt7615_mcu_set_hif_suspend mcu command

Introduce the mt7615_mcu_set_hif_suspend mcu command, which is usually
used to configure the interface including PCIe, USB or SDIO to the right
state during operation suspend / resume.

Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Co-developed-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>