wifi: mt76: disable napi on driver removal

In the Linux kernel, the following vulnerability has been resolved:

wifi: mt76: disable napi on driver removal

A warning on driver removal started occurring after commit 9dd05df8403b

("net: warn if NAPI instance wasn't shut down"). Disable tx napi before

deleting it in mt76_dma_cleanup().

WARNING: CPU: 4 PID: 18828 at net/core/dev.c:7288 __netif_napi_del_locked+0xf0/0x100

CPU: 4 UID: 0 PID: 18828 Comm: modprobe Not tainted 6.15.0-rc4 #4 PREEMPT(lazy)

Hardware name: ASUS System Product Name/PRIME X670E-PRO WIFI, BIOS 3035 09/05/2024

RIP: 0010:__netif_napi_del_locked+0xf0/0x100

Call Trace:

<TASK>

mt76_dma_cleanup+0x54/0x2f0 [mt76]

mt7921_pci_remove+0xd5/0x190 [mt7921e]

pci_device_remove+0x47/0xc0

device_release_driver_internal+0x19e/0x200

driver_detach+0x48/0x90

bus_remove_driver+0x6d/0xf0

pci_unregister_driver+0x2e/0xb0

__do_sys_delete_module.isra.0+0x197/0x2e0

do_syscall_64+0x7b/0x160

entry_SYSCALL_64_after_hwframe+0x76/0x7e

Tested with mt7921e but the same pattern can be actually applied to other

mt76 drivers calling mt76_dma_cleanup() during removal. Tx napi is enabled

in their *_dma_init() functions and only toggled off and on again inside

their suspend/resume/reset paths. So it should be okay to disable tx

napi in such a generic way.

Found by Linux Verification Center (linuxtesting.org).