ipc/util.c: complete the kernel-doc function descriptions

ipc/util.c: complete the kernel-doc function descriptions

Move the function descriptive comments so that they conform to
kernel-doc format, eliminating the kernel-doc warnings.

util.c:618: warning: missing initial short description on line:
 * ipc_obtain_object_idr
util.c:640: warning: missing initial short description on line:
 * ipc_obtain_object_check

Link: https://lkml.kernel.org/r/20250111062905.910576-1-rdunlap@infradead.org
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>