ath10k: call correct function for frag threshold

Rts threshold was being configured instead of
fragmentation threshold.

Keep in mind available firmware binaries don't
seem to support fragmentation anyway so this
doesn't fix fragmentation threshold per se.
Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>

drivers/net/wireless/ath/ath10k/mac.c

@@ -3872,7 +3872,7 @@ static int ath10k_set_frag_threshold(struct ieee80211_hw *hw, u32 value)
 		ath10k_dbg(ar, ATH10K_DBG_MAC, "mac vdev %d fragmentation threshold %d\n",
 			   arvif->vdev_id, value);
 
-		ret = ath10k_mac_set_rts(arvif, value);
+		ret = ath10k_mac_set_frag(arvif, value);
 		if (ret) {
 			ath10k_warn(ar, "failed to set fragmentation threshold for vdev %d: %d\n",
 				    arvif->vdev_id, ret);