ktime: Change ktime_set() to take 64bit seconds value

In order to support dates past 2038 on 32bit systems, ktime_set()
needs to handle 64bit second values.

[ tglx: Removed the BITS_PER_LONG check ]

Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>