Add CMSIS RTOS2 RTX

Change-Id: Ib5a73249809a8ffc91f8624684de07d90c801b87
Signed-off-by: Kevin Peng <kevin.peng@arm.com>
diff --git a/CMSIS/README b/CMSIS/README
new file mode 100644
index 0000000..ff42ebe
--- /dev/null
+++ b/CMSIS/README
@@ -0,0 +1,2 @@
+The files under this folder are copied from:
+https://github.com/ARM-software/CMSIS_5.git, tag 5.5.0, without modifications.