soc/xtensa/intel_adsp/tools: Make cavstool.py DSP resetting more stable

When using more than one core on cavs25, some hangs were made
"persistent", as it seems not all cores were being properly reset, thus
compromising tests - if a test hangs for any reason, subsequent tests
that were not restrict to a single CPU would also fail.

This patch mitigates these issues by two changes:
  - Closely mimics SOF Linux driver way of loading the firmware. So,
    explicit stall and reset (and "unstall" and "unreset") of cores, with
    appropriate checks that states have been reached;
  - More generous sleep before resetting the stream.

Also, the status of ADSPCS (Audio DSP Control and Status) register is
logged more thoroughly to aid debugging in case new issues arise.

Signed-off-by: Ederson de Souza <ederson.desouza@intel.com>