Replace obsolete functions

simple_strtoul/kstrtouint
simple_strtol/kstrtoint
(kstr __must_check requires the right function to be applied)
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Cc: Christine Caulfield <ccaulfie@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>