net: mvneta: fix error path for building skb

net: mvneta: fix error path for building skb

In the actual RX processing, there is same error path for both descriptor
ring refilling and building skb fails. This is not correct, because after
successful refill, the ring is already updated with newly allocated
buffer. Then, in case of build_skb() fail, hitherto code left the original
buffer unmapped.

This patch fixes above situation by swapping error check of skb build with
DMA-unmap of original buffer.

Signed-off-by: Marcin Wojtas <mw@semihalf.com>
Acked-by: Simon Guinot <simon.guinot@sequanux.org>
Cc: <stable@vger.kernel.org> # v4.2+
Fixes a84e32894191 ("net: mvneta: fix refilling for Rx DMA buffers")
Signed-off-by: David S. Miller <davem@davemloft.net>