ath10k: add support for ath10k_sta_statistics support

Enable support for 'drv_sta_statistics' callback.
Export rx_duration support if available to cfg80211/nl80211

This can also act as a placeholder for any new per STA stats support

Signed-off-by: Mohammed Shafi Shajakhan <mohammed@qti.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>