drivers/net/r6040: fix obvious problems (but more remain)

- checkpatch fixes

- fix bogus and uninitialized return codes in r6040_start_xmit()

- netdev_get_settings() fix obvious locking bug flagged by compiler warning

- set DMA consistent mask

- remove unnecessary setting of dev->base_addr

Signed-off-by: Jeff Garzik <jgarzik@redhat.com>