Ethos-U PMU monitor

Add Python script demonstrating how to download performance data
from device.

Write baremetal PMU events to Event Recorder ring buffer and increase
the systick sample rate.

Change-Id: Ib73c56100a8de2d7b74c455d8f80cda0b59383da
diff --git a/.gitignore b/.gitignore
index 796b96d..f284d11 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 /build
+__pycache__