ath9k_hw: set ANI cycpwr_thr1 as absolute values instead of relative

The table was copied from the ANI implementation of AR9300. It assumes
that the INI values contain a baseline value that is usable as reference
from which to increase/decrease based on the noise immunity value.

On older chips, the differences are bigger and especially AR5008/AR9001
are configured to much more sensitive values than what is useful.

Improve ANI behavior by reverting to the absolute values used in the
previous implementation (expressed as a simple formula instead of the
old table).

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>