3c59x: Add dma error checking and recovery

3c59x: Add dma error checking and recovery

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 <[email protected]>
CC: Linux Kernel list <[email protected]>
CC: "David S. Miller" <[email protected]>
CC: Meelis Roos <[email protected]>
Tested-by: Meelis Roos <[email protected]>