Added nnlib-FusionG3 submodule from FOSS-xtensa git space

Signed-off-by: [email protected] <[email protected]>

Author: [email protected]

.gitmodules

@@ -64,3 +64,6 @@
 [submodule "third-party/pybind11"]
 	path = third-party/pybind11
 	url = https://github.com/pybind/pybind11.git
+[submodule "backends/cadence/fusion_g3/third-party/nnlib/nnlib-FusionG3"]
+	path = backends/cadence/fusion_g3/third-party/nnlib/nnlib-FusionG3
+	url = https://github.com/foss-xtensa/nnlib-FusionG3/