mt76: mt7915: simplify conditional

Fix following coccicheck warning:
./drivers/net/wireless/mediatek/mt76/mt7915/mac.c:768:29-31:
WARNING !A || A && B is equivalent to !A || B

Signed-off-by: Wan Jiabing <wanjiabing@vivo.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>