[PATCH] sky2: tx/rx ring data structure split

Split Tx and Rx ring into two different data structures.
Tx needs the next value (to handle partial status), and
Rx always needs the mapaddr (to handle resubmitting same buffer).

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>