MLECO-1933, MLECO-1914, MLECO-1885: Update to 21.05-rc2 components

Core driver and sofware dependencies updated to latest release
candidate revisions. Note: TensorFlow Lite Micro has not been
updated.

Also, gcc warnings for simple_platform target and ad use case have
been fixed.

Change-Id: I455b421f34375a719a941e6e220fe292a57613f5