wifi: ath11k: Fix ath11k_htc_record flexible record

Transform the zero-length ath11k_htc_record::credit_report array into
a proper flexible array. Since this is the only array in
ath11k_htc_record, remove the unnecessary union.

Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20231205-flexarray-htc_record-v2-1-fbb56d436951@quicinc.com

Author: jeff-t-johnson

drivers/net/wireless/ath/ath11k/htc.h

@@ -151,9 +151,7 @@ struct ath11k_htc_credit_report {
 
 struct ath11k_htc_record {
 	struct ath11k_htc_record_hdr hdr;
-	union {
-		struct ath11k_htc_credit_report credit_report[0];
-	};
+	struct ath11k_htc_credit_report credit_report[];
 } __packed __aligned(4);
 
 enum ath11k_htc_svc_gid {