ath9k_hw: sync to latest AR9462 INI

based on systems change to improve rx dynamic range,
and enables heavy clip for 5G HT40 MCS0 to improve
spectral mask power. also remove an unused function
declaration

Cc: Wilson Tsao <wtsao@qca.qualcomm.com>
Signed-off-by: Mohammed Shafi Shajakhan <mohammed@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>