arm64: smp: Fix the wrong secondary core stack size
arm64: smp: Fix the wrong secondary core stack size

The init stack of the secondary core should use KERNEL_STACK_BUFFER + sz
Using Z_THREAD_STACK_BUFFER will calculate the wrong stack size.

Signed-off-by: Jaxson Han <70391990969cde8f4f4c008c74e601e9ed3959a1@arm.com>

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