cpu/hotplug: Delete an extraneous kernel-doc description

struct cpuhp_cpu_state has an extraneous kernel-doc comment for @cpu.
There is no struct member by that name, so remove the comment to
prevent the kernel-doc warning:

  kernel/cpu.c:85: warning: Excess struct member 'cpu' description in 'cpuhp_cpu_state'
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240114030615.30441-1-rdunlap@infradead.org

kernel/cpu.c

@@ -54,7 +54,6 @@
  * @rollback:	Perform a rollback
  * @single:	Single callback invocation
  * @bringup:	Single callback bringup or teardown selector
- * @cpu:	CPU number
  * @node:	Remote CPU node; for multi-instance, do a
  *		single entry callback for install/remove
  * @last:	For multi-instance rollback, remember how far we got