net: sched: Use hrtimer_resolution instead of hrtimer_get_res()

No point in converting a timespec now that the value is directly
accessible.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Link: http://lkml.kernel.org/r/20150414203500.720623028@linutronix.de


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>