Staging: hv: channel: export vmbus_establish_gpadl 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

@@ -584,6 +584,7 @@ Cleanup:
 	kfree(msginfo);
 	return ret;
 }
+EXPORT_SYMBOL_GPL(vmbus_establish_gpadl);
 
 /*
  * vmbus_teardown_gpadl -Teardown the specified GPADL handle