powerpc/rtas: Add kernel-doc comments to smp_startup_cpu()

This commit adds kernel-doc style comments with complete parameter
descriptions for the function smp_startup_cpu().
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240408053109.96360-2-yang.lee@linux.alibaba.com

arch/powerpc/platforms/cell/smp.c

@@ -54,6 +54,7 @@ static cpumask_t of_spin_map;
 
 /**
  * smp_startup_cpu() - start the given cpu
+ * @lcpu: Logical CPU ID of the CPU to be started.
  *
  * At boot time, there is nothing to do for primary threads which were
  * started from Open Firmware.  For anything else, call RTAS with the