Improve ggml backends

diff --git a/sources/ggml b/sources/ggml
index b6bfde39f7b4777c2b24e4deb6ac597883e798dc..3798f56aeed7eab275012be425e8ffbb79eb45e2 160000 (submodule)
--- a/sources/ggml
+++ b/sources/ggml
@@ -1 +1 @@
-Subproject commit b6bfde39f7b4777c2b24e4deb6ac597883e798dc
+Subproject commit 3798f56aeed7eab275012be425e8ffbb79eb45e2