wifi: mt76: mt7915: disable rx napi when removing device

In the Linux kernel, the following vulnerability has been resolved: wifi: mt76: mt7915: disable rx napi when removing device Unloading the mt7915e module with a MT7916 triggers multiples WARN in __netif_napi_del_locked() and in page_pool_disable_direct_recycling() because the driver does not disable the napi before destroying it. This is troublesome since on MT7916 it is required to unload the module and reinsert it with a different enable_6ghz parameter to change the frequency. The system generally becomes unstable after reinserting the module. Fix it by disabling rx napi inside mt7915e itself, even through napi rx is enabled in the mt76 generic code. Disabling it in the mt76 generic code was previously attempted and reverted because napi was disabled too late and rx handlers could access freed structures. Note that the tx side is enabled and disabled by the mt76 generic code. It is disabled in mt7915_stop_hardware() since, unlike mt7915_unregister_device(), is it also called in the probe path if an error happens after rx napi is enabled.