Staging: hv: channel: export vmbus_open 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

@@ -305,6 +305,7 @@ int vmbus_open(struct vmbus_channel *newchannel, u32 send_ringbuffer_size,
 	kfree(openInfo);
 	return err;
 }
+EXPORT_SYMBOL_GPL(vmbus_open);
 
 /*
  * dump_gpadl_body - Dump the gpadl body message to the console for