sched: fair: Reset balance_interval before sending NOHZ kick

balance_interval needs to be reset for anycpu being kicked. Otherwise it
can end up ignoring the kick (i.e not doing load balance for itself).

Also bypass the check for existence of idle cpus in tickless state for
!CONFIG_SCHED_HMP to allow for more aggressive load balance.

Change-Id: I52365ee7c2997ec09bd93c4e9ae0293a954e39a8
Signed-off-by: Srivatsa Vaddagiri <vatsa@codeaurora.org>
Signed-off-by: Syed Rameez Mustafa <rameezmustafa@codeaurora.org>