K 10
svn:author
V 6
adrian
K 8
svn:date
V 27
2012-07-19T02:25:14.505188Z
K 7
svn:log
V 455
Break out the TX descriptor link field into HAL methods.

The DMA FIFO chips (AR93xx and later) differ slightly to th elegacy
chips:

* The RX DMA descriptors don't have a ds_link field;
* The TX DMA descriptors have a ds_link field however at a different
  offset.

This is a reimplementation based on what the reference driver and ath9k
does.

A subsequent commit will enable it in the TX and beacon paths.

Obtained from:	Linux ath9k, Qualcomm Atheros

END