Fix target/ryuglab/linux submodule

We expect to use realtime branch, but master was committed to git.

diff --git a/targets/ryuglab/linux b/targets/ryuglab/linux
index 5aaf6d0c54859a6189cef7f15d74e1f9416c036f..ee765aca15a6765ee4932efb029e70847afb01d6 160000 (submodule)
--- a/targets/ryuglab/linux
+++ b/targets/ryuglab/linux
@@ -1 +1 @@
-Subproject commit 5aaf6d0c54859a6189cef7f15d74e1f9416c036f
+Subproject commit ee765aca15a6765ee4932efb029e70847afb01d6