smp: Add missing kernel-doc comments

smp: Add missing kernel-doc comments

Add missing kernel-doc comments and rearrange the order of others to
prevent all kernel-doc warnings.

 - add function Returns: sections or format existing comments as kernel-doc
 - add missing function parameter comments
 - use "/**" for smp_call_function_any() and on_each_cpu_cond_mask()
 - correct the commented function name for on_each_cpu_cond_mask()
 - use correct format for function short descriptions
 - add all kernel-doc comments for smp_call_on_cpu()
 - remove kernel-doc comments for raw_smp_processor_id() since there is
   no prototype for it here (other than !SMP)
 - in smp.h, rearrange some lines so that the kernel-doc comments for
   smp_processor_id() are immediately before the macro (to prevent
   kernel-doc warnings)
 - remove "Returns" from smp_call_function() since it doesn't
   return a value

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260310061726.1153764-1-rdunlap@infradead.org