sched/fair: fix issue with max_capacity

While integrating 'commit f6df9e00 ("sched: add cpu isolation
support")' merge conflict incorrectly resolved for max_capacity
where min macro used instead of max macro. Correct it by replacing
min with max macro.

Change-Id: I5de97ee92d5d21f8997091457a2eda87c236a741
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>