soc/intel_adsp: Remove cavs/cpu.h
soc/intel_adsp: Remove cavs/cpu.h

Dead code.  Unused in Zephyr.  Seems like SOF is picking this up from
its own headers via reading CONFIG_MP_NUM_CPUS correctly.

Signed-off-by: Andy Ross <c70f9a6bf6ee0cd69c8af4ce5e6b131945769315@intel.com>

finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr