Documentation/timers/hpet_example.c: add supporting info for hpet_example

$./hpet_example info /dev/hpet
-hpet: executing info
hpet_info: hi_irqfreq 0x0 hi_flags 0x0 hi_hpet 0 hi_timer 2

Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com>
Cc: Clemens Ladisch <clemens@ladisch.de>
Cc: "Venkatesh Pallipadi (Venki)" <venki@google.com>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>