Drivers: hv: Simplify data structures for VMBus channel close message

Drivers: hv: Simplify data structures for VMBus channel close message

struct vmbus_close_msg is used for sending the VMBus channel close
message. It contains a struct vmbus_channel_msginfo, which has a
flex array member at the end. The latter's presence in the middle
of struct vmbus_close_msg causes warnings when built with
-Wflex-array-member-not-at-end.

But the struct vmbus_channel_msginfo is unused because the Hyper-V host
does not send a response to the channel close message. So remove the
struct vmbus_channel_msginfo. Then, since the only remaining field is
struct vmbus_channel_close_channel, also remove the containing struct
vmbus_close_msg and directly use struct vmbus_channel_close_channel.
Besides eliminating unnecessary complexity, these changes resolve the
-Wflex-array-member-not-at-end warnings.

Signed-off-by: Michael Kelley <mhklinux@outlook.com>
Reviewed-by: Tianyu Lan <tiala@microsoft.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>