net: cavium: liquidio: Avoid dma_unmap_single on uninitialized ndata

The label lio_xmit_failed is used 3 times through liquidio_xmit() but it
always makes a call to dma_unmap_single() using potentially
uninitialized variables from "ndata" variable. Out of the 3 gotos, 2 run
after ndata has been initialized, and had a prior dma_map_single() call.

Fix this by adding a new error label: lio_xmit_dma_failed which does
this dma_unmap_single() and then processed with the lio_xmit_failed
fallthrough.

Fixes: f21fb3ed ("Add support of Cavium Liquidio ethernet adapters")
Reported-by: coverity (CID 1309740)
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>