ath10k: align ath10k_htt_txbuf structures

With W=1 GCC warns:

drivers/net/wireless/ath/ath10k/htt.h:1746:1: warning: alignment 1 of 'struct ath10k_htt_txbuf_32' is less than 4 [-Wpacked-not-aligned]
drivers/net/wireless/ath/ath10k/htt.h:1753:1: warning: alignment 1 of 'struct ath10k_htt_txbuf_64' is less than 4 [-Wpacked-not-aligned]

Fix that by using __align(4). Compile tested only.
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

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

@@ -1743,14 +1743,14 @@ struct ath10k_htt_txbuf_32 {
 	struct ath10k_htc_hdr htc_hdr;
 	struct htt_cmd_hdr cmd_hdr;
 	struct htt_data_tx_desc cmd_tx;
-} __packed;
+} __packed __aligned(4);
 
 struct ath10k_htt_txbuf_64 {
 	struct htt_data_tx_desc_frag frags[2];
 	struct ath10k_htc_hdr htc_hdr;
 	struct htt_cmd_hdr cmd_hdr;
 	struct htt_data_tx_desc_64 cmd_tx;
-} __packed;
+} __packed __aligned(4);
 
 struct ath10k_htt {
 	struct ath10k *ar;