Update pulp-nn-mixed submodule (pulp-platform#145)

This PR updates the `pulp-nn-mixed` submodule to include the fix for an illegal hardware loop configuration related to the `pulp_zero_mem` utility function [PR10](pulp-platform/pulp-nn-mixed#10). The updated submodule removes the MemoryFence() from the loop, allowing the compiler to correctly generate a valid HW loop and preventing illegal configurations.

## Changed
- `pulp-nn-mixed` submodule

Author: marchioa

CHANGELOG.md

@@ -4,6 +4,7 @@ This file contains the changelog for the Deeploy project. The changelog is divid
 ## Unreleased (Planned Release Target: v0.2.1)
 
 ### List of Pull Requests
+- Update submodule `pulp-nn-mixed` [#145](https://github.com/pulp-platform/Deeploy/pull/145)
 - Improve Profiling [#138](https://github.com/pulp-platform/Deeploy/pull/138)
 - FP32 ReduceMean operator improvement [#137](https://github.com/pulp-platform/Deeploy/pull/137)
 - Support for RMSNorm (Pow and Sqrt operators) [#136](https://github.com/pulp-platform/Deeploy/pull/136)