cpu/hotplug: Provide weak fallback for arch_cpuhp_init_parallel_bringup()

CONFIG_HOTPLUG_PARALLEL expects the architecture to implement
arch_cpuhp_init_parallel_bringup() to decide whether paralllel hotplug is
possible and to do the necessary architecture specific initialization.

There are architectures which can enable it unconditionally and do not
require architecture specific initialization.

Provide a weak fallback for arch_cpuhp_init_parallel_bringup() so that
such architectures are not forced to implement empty stub functions.

Signed-off-by: Jiaxun Yang <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/all/[email protected]

Author: FlyGoat

kernel/cpu.c

@@ -1829,6 +1829,11 @@ static inline const struct cpumask *cpuhp_get_primary_thread_mask(void)
 }
 #endif
 
+bool __weak arch_cpuhp_init_parallel_bringup(void)
+{
+	return true;
+}
+
 /*
  * On architectures which have enabled parallel bringup this invokes all BP
  * prepare states for each of the to be onlined APs first. The last state