Fix: Use MAX_RT_PRIO offset in sched_wakeup_template

All other sched_* events with prio fields offset the task_struct's
prio value by subtracting MAX_RT_PRIO. This way the value corresponds
to that given by the kernel's task_prio function, and thus with the
prio context field.

This adds the same offset to sched_wakeup, sched_wakeup_new, and
sched_waking, via the sched_wakeup_template event class. This way
their value is comparable to other sched_* events, and the prio
context.

Signed-off-by: Antoine Busque <abusque@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>