cpu: Fix W=1 build kernel-doc warning

Building the kernel with W=1 generates the following warning:

  kernel/cpu.c:2693: warning: This comment starts with '/**',
  		     but isn't a kernel-doc comment.

The function topology_is_core_online() is a simple helper function and
doesn't need a kernel-doc comment.

Use a normal comment instead.
Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240825221152.71951-2-thorsten.blum@toblux.com

kernel/cpu.c

@@ -2705,9 +2705,7 @@ int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
 	return ret;
 }
 
-/**
- * Check if the core a CPU belongs to is online
- */
+/* Check if the core a CPU belongs to is online */
 #if !defined(topology_is_core_online)
 static inline bool topology_is_core_online(unsigned int cpu)
 {