soc: xtensa: intel_adsp: add missing init.h

Some files were using SYS_INIT without including init.h.

Signed-off-by: Gerard Marull-Paretas <gerard@teslabs.com>

soc/xtensa/intel_adsp/ace/multiprocessing.c

@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
+#include <zephyr/init.h>
 #include <zephyr/kernel.h>
 #include <zephyr/sys/check.h>
 #include <zephyr/arch/cpu.h>

soc/xtensa/intel_adsp/common/boot_complete.c

@@ -5,6 +5,7 @@
 #include <zephyr/arch/xtensa/arch.h>
 #include <zephyr/device.h>
 #include <zephyr/devicetree.h>
+#include <zephyr/init.h>
 #include <errno.h>
 #include <soc.h>