net: stmmac: fix dma mapping leak in stmmac_tso_xmit()

In the Linux kernel, the following vulnerability has been resolved: net: stmmac: fix dma mapping leak in stmmac_tso_xmit() In stmmac_tso_xmit(), if the DMA mapping of an skb fragment fails, the frame is dropped but the DMA mappings already created for the linear part and for the fragments mapped before the failure are never unmapped, leaking DMA mappings. Fix the leak by walking back over the descriptors used by the frame and releasing each of them with stmmac_free_tx_buffer(). Moreover, release the descriptors with stmmac_release_tx_desc() unmapping the DMA buffers.