e100: Release skb when DMA mapping is failed in e100_xmit_prepare
e100: Release skb when DMA mapping is failed in e100_xmit_prepare

When pci_dma_mapping_error in e100_xmit_prepare is failed, the skb buffer
allocated by netdev_alloc_skb_ip_align in e100_rx_alloc_skb is not
released, which causes a possible resource leak.
This patch adds error handling code to fix it.

Signed-off-by: Jia-Ju Bai <4f6d392e422d1b8f381e5a7c1b9b3c46d9851e8b@163.com>
Tested-by: Aaron Brown <4723df1d9a4136f7b76e1bf6434e33afc91d2139@intel.com>
Signed-off-by: Jeff Kirsher <87e35f5be20bb3e67f4ba6b86f5f6be3085b1b3a@intel.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs