soc/intel_adsp: XTENSA_WAITI_BUG must be set of cAVS1.8 and newer

Align definitions with definitions used in SOF upstream and define
CONFIG_XTENSA_WAITI_BUG for cAVS1.8, cAVS2.0 and cAVS2.5 platforms. On
these platforms, a workaround is needed with waiti.

Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>