Use hrtimer instead of the normal timer, since it provides better
sampling resolution. This will:

- avoid a problem where we have a 1 jiffy poll period and dynamic tick on
- utilize high resolution HW clocks when they are added to the hrtimer
  framework
Signed-off-by: Imre Deak <imre.deak@solidboot.com>
Signed-off-by: Juha Yrjola <juha.yrjola@solidboot.com>