Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

[net80211] Begin implementing rate control module stats.

* Implement a new ratectl method, which defaults to returning nothing;
* Add a top level sysctl (net.wlan.X.rate_stats) to extract it;
* Add ratectl info for the 'amrr' module.

Tested:

* urtwn(4), STA mode

Differential Revision: https://reviews.freebsd.org/D5630

Switch around the order of static inline to be in line with how it's
used elsewhere, and to keep gcc-4.7 happy.

This is a request from the DragonflyBSD project.

The ni_rctls checks are used to verify that a ratectl algo has set up
its internal data. This has been used to bypass missing calls in drivers
which do not use the ratectl framework correctly. Issue is, not all algos
use that variable, or even have internal data, therefore valid calls are
not done. Fix this by removing the checks, all driver issues should be
resolved.

MFC after: 1 week

Instead of using the AMRR ratectl algo as default for drivers which have
the IEEE80211_C_RATECTL flag set, default to NONE for all drivers. Only if
a driver calls ieee80211_ratectl_init() check if the NONE algo is still
selected and try to use AMRR in that case. Drivers are still free to use
any other algo by calling ieee80211_ratectl_set() prior to the
ieee80211_ratectl_init() call.

After this change it is now safe to assume that a ratectl algo is always
available and selected, which renders the IEEE80211_C_RATECTL flag pretty
much useless. Therefore revert r211314 and 211546.

Reviewed by: rpaulo
MFC after: 2 weeks

Fix an undefined behaviour if the desired ratectl algo is not available.
This can happen if the algos are built as modules but are not loaded. If
the selected ratectl algo is not available, try to load it (The load
module functions does nothing currently). Add a dummy ratectl algo which
always selects the first available rate. Use that one if the desired algo
is not available.

MFC after: 1 week

Swap IEEE80211_RATECTL_TX_SUCCESS/IEEE80211_RATECTL_TX_FAILURE.

Submitted by: PseudoCylon Furukoshi <moonlightakkiy at yahoo.ca>
MFC after: 1 month

Prevent foot-shooting in ieee80211_ratectl_node_deinit().

MFC after: 1 month

Fix build.

Pointy hat: me
MFC after: 1 month

net80211 rate control framework (net80211 ratectl).

This framework allows drivers to abstract the rate control algorithm and
just feed the framework with the usable parameters. The rate control
framework will now deal with passing the parameters to the selected
algorithm. Right now we have AMRR (the default) and RSSADAPT but there's
no way to select one with ifconfig, yet.
The objective is to have more rate control algorithms in the net80211
stack so all drivers[0] can use it. Ideally, we'll have the well-known
sample rate control algorithm in the net80211 at some point so all
drivers can use it (not just ath).

[0] all drivers that do rate control in software, that is.

Reviewed by: bschmidt, thompsa, weyongo
MFC after: 1 months