Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC: r243857 (partial)

Mechanically substitute flags from historic mbuf allocator with
malloc(9) flags in sys/dev.

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Add in HT protection but disable it by default.

I'll clear how it's supposed to work with Bernhard and then look
at enabling this in the correct situations.

But this -does- enable HT RTS protection (using the appropriate legacy
rates) if this bit of code is enabled.

Shuffle around the RTS/CTS rate/duration logic.

* Turn ath_tx_calc_ctsduration() into a function that
returns the ctsduration, or -1 for HT rates;
* add a printf() to ath_tx_calc_ctsduration() which will be
very loud if somehow that function is called with an MCS
rate;
* Add ath_tx_get_rtscts_rate() which returns the RTS/CTS
rate to use for the given data rate, incl. the short
preamble flag;
* Only call ath_tx_calc_ctsduration() for non-11n chipsets;
11n chipsets don't require the rtscts duration to be
calculated.

The current code used the fields in ath_set11nratescenario() . Use them
correctly:

* pass in whether to allow the hardware to override the duration field
in the main data frame (durupdate_en) - PS_POLL frames in particular
don't have the duration bit overriden;
* there's no rts/cts duration here; that's done elsehwere

Modify the TX path to set and use the 11n rate scenario bits.

This isn't strictly required to TX (at least non-agg and non-HT40,
non-short-GI) frames; but as it needs to be done anyway, just get
it done.

Linux ath9k uses the rate scenario style path for -all- packets,
legacy or otherwise. This code does much the same.

Beacon TX still uses the legacy, non-rate-scenario TX descriptor
setup. Ath9k also does this.

This 11n rate scenario path is only called for chips in the AR5416
HAL; legacy chips use the previous interface for TX'ing.

Refator the common code which calculates the 802.11g protection duration.

* Add a rather hacky "does this speak the 11n TX descriptor format"
function; which will be later used by the TX path to determine
whether to use the extended features or not.

* Break out the descriptor chaining logic into a separate function;
again so it can be switched out later on for the 11n version when
needed.

* Refactor out the encryption-swizzling code that's common in the
raw and normal TX path.

Migrate the TX path code out of if_ath and into a separate source file.

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.