mt76: use skb_pad() instead of __skb_pad()

mt76 uses __skb_pad() with free_on_error set to true, this is the same
as calling skb_pad().
This patch does not change any functionality, but it makes it easier to
backport this driver in backports, because skb_pad() is also available
in older kernel versions.

Fixes: b40b15e1 ("mt76: add usb support to mt76 layer")
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt76x02_usb_core.c

@@ -43,7 +43,7 @@ int mt76x02u_skb_dma_info(struct sk_buff *skb, int port, u32 flags)
 	}
 
 	if (unlikely(pad)) {
-		if (__skb_pad(last, pad, true))
+		if (skb_pad(last, pad))
 			return -ENOMEM;
 		__skb_put(last, pad);
 	}