hrtimer: Add hrtimer support for CLOCK_TAI

Add hrtimer support for CLOCK_TAI, as well as posix timer interfaces.

Signed-off-by: John Stultz <john.stultz@linaro.org>

include/linux/timekeeper_internal.h

@@ -64,6 +64,8 @@ struct timekeeper {
 	struct timespec		raw_time;
 	/* The current UTC to TAI offset in seconds */
 	s32			tai_offset;
+	/* Offset clock monotonic -> clock tai */
+	ktime_t			offs_tai;
 
 	/* Seqlock for all timekeeper values */
 	seqlock_t		lock;