wifi: mt76: mt7921: fix PCI DMA hang after reboot

mt7921 just stop some workers and clean up chip status before reboot.
In stress test, there are working activities still running at the period
of .shutdown callback and that would cause some hosts cannot recover
DMA after reboot. To avoid the floating state in reboot, we use
mt7921_pci_remove() to fully deinit all resources.

Fixes: f23a0cea ("wifi: mt76: mt7921e: add pci .shutdown() support")
Signed-off-by: Deren Wu <deren.wu@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>