Add cmsis-dsp in repository's ignore list

Change-Id: Ie19178905af511a1117c8501ec1c84d1c996a94c
diff --git a/.gitignore b/.gitignore
index 7c5676a..79ba722 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,7 @@
 /build
 /core_driver
 /cmsis
+/cmsis-dsp
 /cmsis-nn
 /rtos/freertos
 /rtos/threadx