staging: ozwpan: High resolution timers

Current implementation assumes HZ = 1000 for calculating
all internal timer intervals, which creates problem on
platforms where HZ != 1000.

As well we need resolution of less than 10 mSec for heartbeat
calculation, this creates problem on some platforms where HZ is
configured as HZ = 100, or around, which restricts us to timer interval
of 10 mSec. This is particularly found on embedded devices.

This patch moves on to use high resolution timers to calculate
all timer intervals as it allows us to have very small resolution
of timer interval, removing dependency on HZ.

Signed-off-by: Rupesh Gujare <rupesh.gujare@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>