vmxnet3: fix checks for dma mapping errors

vmxnet3_drv does not check dma_addr with dma_mapping_error()
after mapping dma memory. The patch adds the checks and
tries to handle failures.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Acked-by: Shrikrishna Khare <skhare@vmware.com>
Signed-off-by: David S. Miller <davem@davemloft.net>