hv_netvsc: Replace one-element array with flexible array member

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: https://github.com/KSPP/linux/issues/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>