sched/hmp: Disable interrupts when resetting all task stats

Taking the pi_lock without disabling interrupts in reset_all_task_stats()
is problematic. In that an interrupt can end up waking a task which in
turn needs the pi_lock again causing a deadlock. Disable interrupts along
with taking the lock to avoid this problem.

Change-Id: If27cb2bb3fcaafa5c8435f3c2e0e4be9b8f1e987
Signed-off-by: Syed Rameez Mustafa <rameezmustafa@codeaurora.org>