mm/kmemleak: replace strncpy() with strscpy()

Replace the depreciated[1] strncpy() calls with strscpy().  Uses of
object->comm do not depend on the padding side-effect.

Link: https://github.com/KSPP/linux/issues/90 [1]
Link: https://lkml.kernel.org/r/20240710001300.work.004-kees@kernel.org


Signed-off-by: Kees Cook <kees@kernel.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>