ath9k: add new ANI implementation for AR9003

ath9k: add new ANI implementation for AR9003

This adds support for ANI for AR9003. The implementation for
ANI for AR9003 is slightly different than the one used for
the older chipset families. It can technically be used for
the older families as well but this is not yet fully tested
so we only enable the new ANI for the AR5008, AR9001 and AR9002
families with a module parameter, force_new_ani.

The old ANI implementation is left intact.

Details of the new ANI implemention:

  * ANI adjustment logic is now table driven so that each ANI level
    setting is parameterized. This makes adjustments much more
    deterministic than the old procedure based logic and allows
    adjustments to be made incrementally to several parameters per
    level.

  * ANI register settings are now relative to INI values; so ANI
    param zero level == INI value. Appropriate floor and ceiling
    values are obeyed when adjustments are combined with INI values.

  * ANI processing is done once per second rather that every 100ms.
    The poll interval is now a set upon hardware initialization and
    can be picked up by the core driver.

  * OFDM error and CCK error processing are made in a round robin
    fashion rather than allowing all OFDM adjustments to be made
    before CCK adjustments.

  * ANI adjusts MRC CCK off in the presence of high CCK errors

  * When adjusting spur immunity (SI) and OFDM weak signal detection,
    ANI now sets register values for the extension channel too

  * When adjusting FIR step (ST), ANI now sets register for FIR step
    low too

  * FIR step adjustments now allow for an extra level of immunity for
    extremely noisy environments

  * The old Noise immunity setting (NI), which changes coarse low, size
    desired, etc have been removed. Changing these settings could affect
    up RIFS RX as well.

  * CCK weak signal adjustment is no longer used

  * ANI no longer enables phy error interrupts; in all cases phy hw
    counting registers are used instead

  * The phy error count (overflow) interrupts are also no longer used
    for ANI adjustments. All ANI adjustments are made via the polling
    routine and no adjustments are possible in the ISR context anymore

  * A history settings buffer is now correctly used for each channel;
    channel settings are initialized with the defaults but later
    changes are restored when returning back to that channel

  * When scanning, ANI is disabled settings are returned to (INI) defaults.

  * OFDM phy error thresholds are now 400 & 1000 (errors/second units) for
    low/high water marks, providing increased stability/hysteresis when
    changing levels.

  * Similarly CCK phy error thresholds are now 300 & 600 (errors/second)

Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>