timer: Use variable head instead of &work_list in __run_timers()

We already have a variable 'head' that points to '&work_list', and so
we should use that instead wherever possible.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: linaro-kernel@lists.linaro.org
Link: http://lkml.kernel.org/r/0d8645a6efc8360c4196c9797d59343abbfdcc5e.1395129136.git.viresh.kumar@linaro.org


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