mt76: mt7915: fix twt table_mask to u16 in mt7915_dev

mt7915 can support 16 twt stations so modify table_mask to u16.

Fixes: 3782b69d ("mt76: mt7915: introduce mt7915_mac_add_twt_setup routine")
Signed-off-by: Peter Chiu <chui-hao.chiu@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt7915/mt7915.h

@@ -319,7 +319,7 @@ struct mt7915_dev {
 	void *cal;
 
 	struct {
-		u8 table_mask;
+		u16 table_mask;
 		u8 n_agrt;
 	} twt;