Fixes gcc '-Wunused-but-set-variable' warning:
drivers/net/wireless/mediatek/mt76/dma.c: In function mt76_dma_rx_fill:
drivers/net/wireless/mediatek/mt76/dma.c:377:6: warning: variable idx set but not used [-Wunused-but-set-variable]
It is not used since commit 
17f1de56df05 ("mt76:
add common code shared between multiple chipsets")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
 
        int frames = 0;
        int len = SKB_WITH_OVERHEAD(q->buf_size);
        int offset = q->buf_offset;
-       int idx;
 
        spin_lock_bh(&q->lock);
 
 
                qbuf.addr = addr + offset;
                qbuf.len = len - offset;
-               idx = mt76_dma_add_buf(dev, q, &qbuf, 1, 0, buf, NULL);
+               mt76_dma_add_buf(dev, q, &qbuf, 1, 0, buf, NULL);
                frames++;
        }