net: wwan: t7xx: Fix off-by-one error in t7xx_dpmaif_rx_buf_alloc()

The error path in t7xx_dpmaif_rx_buf_alloc(), free and unmap the already
allocated and mapped skb in a loop, but the loop condition terminates when
the index reaches zero, which fails to free the first allocated skb at
index zero.

Check with i-- so that skb at index 0 is freed as well.

Cc: [e-mail]
Fixes: d642b012df70 ("net: wwan: t7xx: Add data path interface")
Acked-by: Sergey Ryazanov <[e-mail]>
Signed-off-by: Jinjie Ruan <[e-mail]>
Reviewed-by: Ilpo Järvinen <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/wwan/t7xx/t7xx_hif_dpmaif_rx.c

···
 	return 0;
 
 err_unmap_skbs:
-	while (--i > 0)
+	while (i--)
 		t7xx_unmap_bat_skb(dpmaif_ctrl->dev, bat_req->bat_skb, i);
 
 	return ret;