ath10k: prefer kernel type 'u64' over 'u_int64_t'

Fixes checkpatch warnings:

drivers/net/wireless/ath/ath10k/htt.h:1477: Prefer kernel type 'u64' over 'u_int64_t'
drivers/net/wireless/ath/ath10k/htt.h:1480: Prefer kernel type 'u64' over 'u_int64_t'

Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>

drivers/net/wireless/ath/ath10k/htt.h

@@ -1475,10 +1475,10 @@ union htt_rx_pn_t {
 	u32 pn24;
 
 	/* TKIP or CCMP: 48-bit PN */
-	u_int64_t pn48;
+	u64 pn48;
 
 	/* WAPI: 128-bit PN */
-	u_int64_t pn128[2];
+	u64 pn128[2];
 };
 
 struct htt_cmd {