Revert "ktime: Simplify ktime_compare implementation"

Thierry bisected boot failures to this simplification commit.

Reverts: 3f1d4720 ("ktime: Simplify ktime_compare implementation")
Reported-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Mariusz Skamra <mariuszx.skamra@intel.com>