ath10k: remove MAC80211_DEBUGFS dependency on ath10k_sta_statistics

Remove CONFIG_MAC80211_DEBUGFS dependency on ath10k_sta_statistics().
ath10k_sta_statistics() has per sta tx/rx stats and this should not
be dependent on MAC80211_DEBUGFS.

No changes in functionality.

Signed-off-by: Anilkumar Kolli <akolli@qti.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>