pw_stm32cube_build: Add DSP include dir

Change-Id: I22831dd59cf3201520deb3e8a4f029ea7abd9d3b
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/84606
Pigweed-Auto-Submit: Armando Montanez <amontanez@google.com>
Reviewed-by: Anthony DiGirolamo <tonymd@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/pw_stm32cube_build/py/pw_stm32cube_build/find_files.py b/pw_stm32cube_build/py/pw_stm32cube_build/find_files.py
index 903c05b..6e233ef 100644
--- a/pw_stm32cube_build/py/pw_stm32cube_build/find_files.py
+++ b/pw_stm32cube_build/py/pw_stm32cube_build/find_files.py
@@ -209,6 +209,7 @@
     'hal_driver/Inc/Legacy',
     'cmsis_device/Include',
     'cmsis_core/Include',
+    'cmsis_core/DSP/Include',
 ]