Noted that 3c59x has no checks on transmit for failed DMA mappings, and no
ability to unmap fragments when a single map fails in the middle of a transmit.
This patch provides error checking to ensure that dma mappings work properly,
and unrolls an skb mapping if a fragmented skb transmission has a mapping
failure to prevent leaks.
Signed-off-by: Neil Horman <nhorman@tuxdriver.com> CC: Linux Kernel list <linux-kernel@vger.kernel.org> CC: "David S. Miller" <davem@davemloft.net> CC: Meelis Roos <mroos@linux.ee> Tested-by: Meelis Roos <mroos@linux.ee>