include/linux/slub_def.h: comment fixes

Capitialize comment string, use C89 comment style, correct
grammar/punctuation in comments.

Link: http://lkml.kernel.org/r/20190204005713.9463-2-tobin@kernel.org
Link: http://lkml.kernel.org/r/20190204005713.9463-3-tobin@kernel.org
Link: http://lkml.kernel.org/r/20190204005713.9463-4-tobin@kernel.org


Signed-off-by: Tobin C. Harding <tobin@kernel.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>