hv_netvsc: Replace one-element array with flexible array member

Replace the deprecated one-element array with a modern flexible array
member in the struct nvsp_1_message_send_receive_buffer_complete.

Use struct_size_t(,,1) instead of sizeof() to maintain the same size.

Compile-tested only.

Link: KSPP#79
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Tested-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Roman Kisel <romank@linux.microsoft.com>
Link: https://patch.msgid.link/20250116211932.139564-2-thorsten.blum@linux.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: toblux

drivers/net/hyperv/hyperv_net.h

@@ -464,7 +464,7 @@ struct nvsp_1_message_send_receive_buffer_complete {
 	 *  LargeOffset                            SmallOffset
 	 */
 
-	struct nvsp_1_receive_buffer_section sections[1];
+	struct nvsp_1_receive_buffer_section sections[];
 } __packed;
 
 /*

drivers/net/hyperv/netvsc.c

@@ -866,7 +866,8 @@ static void netvsc_send_completion(struct net_device *ndev,
 
 	case NVSP_MSG1_TYPE_SEND_RECV_BUF_COMPLETE:
 		if (msglen < sizeof(struct nvsp_message_header) +
-				sizeof(struct nvsp_1_message_send_receive_buffer_complete)) {
+				struct_size_t(struct nvsp_1_message_send_receive_buffer_complete,
+					      sections, 1)) {
 			netdev_err(ndev, "nvsp_msg1 length too small: %u\n",
 				   msglen);
 			return;