Staging: hv: channel: export vmbus_close to modules

Drivers need to call this directly, so export it, like other
vmbus functions.

Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Hank Janssen <hjanssen@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/hv/channel.c

@@ -703,6 +703,7 @@ void vmbus_close(struct vmbus_channel *channel)
 		free_channel(channel);
 	}
 }
+EXPORT_SYMBOL_GPL(vmbus_close);
 
 /**
  * vmbus_sendpacket() - Send the specified buffer on the given channel