sched: Delete is_same_group() outside CONFIG_FAIR_GROUP_SCHED

Since is_same_group() is only used in the group scheduling code, there is
no need to define it outside CONFIG_FAIR_GROUP_SCHED.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1391005773-29493-1-git-send-email-dietmar.eggemann@arm.com


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