arm64: fix stack pointer initialization when CONFIG_STACK_COLORATION disabled

Add else clause to advance stack pointer (x24) by SMP_STACK_SIZE when
CONFIG_STACK_COLORATION is not defined in ARM64 boot code. Ensures each
CPU's stack is properly skipped in multi-core initialization even when
stack coloration/validation is disabled, preventing stack corruption from
overlapping CPU stacks.

Signed-off-by: hujun5 <hujun5@xiaomi.com>

arch/arm64/src/common/arm64_head.S

@@ -179,6 +179,8 @@ real_start:
     str    w2, [x24], #4
     cmp    w1, #0
     bne    .loop
+#  else
+    add    x24, x24, #(SMP_STACK_SIZE)
 #  endif
 
     /* Initialize percpu reg tpidr_el1 */