platform: replace strict_strto*() with kstrto*()

The usage of strict_strtoul() and strict_strtol() is not preferred,
because strict_strtoul() and strict_strtol() are obsolete. Thus,
kstrtoul() and kstrtol() should be used.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>