sched/fair: Fix comment in calculate_imbalance()

The comment in calculate_imbalance() was introduced in commit:

 2dd73a4f ("[PATCH] sched: implement smpnice")

which described the logic as it was then, but a later commit:

  b1885550 ("sched/balancing: Fix 'local->avg_load > sds->avg_load' case in calculate_imbalance()")

.. complicated this logic some more so that the comment does not match anymore.

Update the comment to match the code.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1461958364-675-3-git-send-email-dietmar.eggemann@arm.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>