autobot: Update open-iot-sdk

Update open-iot-sdk to 15e24e3e32b8e862df386e0b0a38e3e0a6d2a8c0.

To make the examples compatible with the latest Open IoT SDK, we also
* update configuration variables and test logs to match TF-M v1.7
* enable Helium (MVE) by default, because the current CMSIS-DSP has a
bug that fails the build when we turn off Helium for a processor that
supports Helium

Signed-off-by: autobot <autobot-noreply@arm.com>
Signed-off-by: Lingkai Dong <lingkai.dong@arm.com>