reorder struct hrtimer to save 8 bytes on 64 bit builds when
CONFIG_TIMER_STATS selected.  (also removes 8 bytes from signal_struct)
Signed-off-by: NRichard Kennedy <richard@rsk.demon.co.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>