* Immediately return NULL if a buffer isn't available;
* Track the "buffers not available" count;
* Clear some fields used for tx aggregation;
* Add ath_buf_clone() which clones the majority of buffer state.
This is needed when retransmission of a "busy" buffer is required.
Sponsored by: Hobnob, Inc.
and interface resets to be marked as ATH_RESET_DEFAULT, ATH_RESET_FULL,
ATH_RESET_NOLOSS.
Currently a reset is still a reset - ie, all tx/rx frames in the hardware
queues are purged. This means that those frames will be lost to the 11n TX
and RX aggregation state tracking, breaking AMPDU sessions.
The (eventual) new semantics:
* ATH_RESET_DEFAULT:
full reset, this is the default for reset situations
which I haven't yet figured out what they should be.
* ATH_RESET_FULL:
A full reset - for things such as channel changes.
* ATH_RESET_NOLOSS:
Don't flush TX/RX queues - handle pending RX frames and leave TX
frames where they are; restart TX DMA from where it was.
There's two reasons for this:
* the raw and non-raw TX path shares a lot of duplicate code which should be
refactored;
* the 11n-ready chip TX path needs a little reworking.
