mt76: mt7921: avoid unnecessary consecutive WiFi resets

Avoid unnecessary consecutive WiFi resets by dropping reset
request when reset work is working.

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