mt76: mt7615: fix sparse warnings: warning: restricted __le16 degrades to integer

Fix the following sparse warning in __mt7615_mcu_msg_send:
drivers/net/wireless/mediatek/mt76/mt7615/mcu.c:78:15: sparse: warning:
restricted __le16 degrades to integer
drivers/net/wireless/mediatek/mt76/mt7615/mcu.c:78:15: sparse: warning:
cast from restricted __le16

Fixes: 04b8e659 ("mt76: add mac80211 driver for MT7615 PCIe-based chipsets")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt7615/mcu.c

@@ -75,7 +75,7 @@ static int __mt7615_mcu_msg_send(struct mt7615_dev *dev, struct sk_buff *skb,
 
 	txd = mcu_txd->txd;
 
-	val = FIELD_PREP(MT_TXD0_TX_BYTES, cpu_to_le16(skb->len)) |
+	val = FIELD_PREP(MT_TXD0_TX_BYTES, skb->len) |
 	      FIELD_PREP(MT_TXD0_P_IDX, MT_TX_PORT_IDX_MCU) |
 	      FIELD_PREP(MT_TXD0_Q_IDX, q_idx);
 	txd[0] = cpu_to_le32(val);