wifi: mt76: mt7925: Simplify HIF suspend handling to avoid suspend fail

wifi: mt76: mt7925: Simplify HIF suspend handling to avoid suspend fail

System suspend failures may occur due to inappropriate
handling of traffic not idle event by the WiFi driver.
The WiFi firmware's traffic not idle indication does
not need to be tied to suspend. Fix the flow to ensuring
the system can suspend properly.

Signed-off-by: Quan Zhou <quan.zhou@mediatek.com>
Link: https://patch.msgid.link/34208c7280325f57a651363d339399eb1744d3b7.1740400998.git.quan.zhou@mediatek.com
Signed-off-by: Felix Fietkau <nbd@nbd.name>