wil6210: add support for enhanced DMA TX data flows

The enhanced DMA TX data path is handled using a descriptor
ring per connection and a single status ring.

The driver gets TX completions via the TX status ring. Each
status message points to the completed descriptor ring and
includes the number of completed descriptors in this ring.

Non TSO enhanced DMA TX descriptors are similar to legacy DMA
TX descriptors, hence the same transmit function can be used.

However, enhanced DMA TSO frames division is performed by the
HW, hence a new function is added to handle enhanced DMA TSO.

Change-Id: I5049c5c2dc062e11334faae0ef6d45ed712882c8
Signed-off-by: Gidon Studinski <gidons@codeaurora.org>
Signed-off-by: Maya Erez <merez@codeaurora.org>