time: Consolidate the time accessor prototypes

Right now we have time related prototypes in 3 different header
files. Move it to a single timekeeping header file and move the core
internal stuff into a core private header.

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

diff --cc include/linux/hrtimer.h
Simple merge

diff --cc include/linux/ktime.h
Simple merge

diff --cc include/linux/time.h
Simple merge

diff --cc include/linux/timekeeping.h
Simple merge

diff --cc kernel/time/hrtimer.c
Simple merge

diff --cc kernel/time/posix-timers.c
Simple merge

diff --cc kernel/time/tick-internal.h
Simple merge

diff --cc kernel/time/time.c
Simple merge

diff --cc kernel/time/timekeeping.h
Simple merge