kernel: cleanup and formally define CPU start fn

The "key" parameter is legacy, remove it.

Add a typedef for the expected function pointer type.

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>

include/sys/arch_interface.h

@@ -159,6 +159,13 @@ void arch_cpu_atomic_idle(unsigned int key);
  * @{
  */
 
+/**
+ * Per-cpu entry function
+ *
+ * @param context parameter, implementation specific
+ */
+typedef FUNC_NORETURN void (*arch_cpustart_t)(void *data);
+
 /**
  * @brief Start a numbered CPU on a MP-capable system
  *
@@ -176,12 +183,11 @@ void arch_cpu_atomic_idle(unsigned int key);
  * @param cpu_num Integer number of the CPU
  * @param stack Stack memory for the CPU
  * @param sz Stack buffer size, in bytes
- * @param fn Function to begin running on the CPU.  First argument is
- *        an irq_unlock() key.
+ * @param fn Function to begin running on the CPU.
  * @param arg Untyped argument to be passed to "fn"
  */
 void arch_start_cpu(int cpu_num, k_thread_stack_t *stack, int sz,
-		    void (*fn)(int key, void *data), void *arg);
+		    arch_cpustart_t fn, void *arg);
 /** @} */