LinuxKPI: add time_is_after_jiffies() definition

This is used by wireless drivers. Use the time_after() macro as
done for the "after_eq" version.

Sponsored by: The FreeBSD Foundation
Reviewed by: hselasky
Differential Revision: https://reviews.freebsd.org/D30430

(cherry picked from commit 8620fe4c10922b12492155d97b913deb6c5d82c6)