sched/core: fix warning from _nohz_idle_balance() after core unisolation

A warning is introduced by commit 92d7dde0
("sched: add cpu isolation support") in the unisolation path due to
usage of NOHZ_BALANCE_KICK. After core is unisolated, we try to kick
CPU to do load balancing using NOHZ_BALANCE_KICK, but,
commit b7031a02 ("sched/fair: Add NOHZ_STATS_KICK")
separated stats and actual kick which forces to use NOHZ_KICK_MASK
instead of NOHZ_BALANCE_KICK.

Change-Id: I0c0e90ac8f814dbfbaac00a680db8510a5587b6d
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>