sched: Fix sched_mv_power_savings for !SMT

Fix for sched_mc_powersavigs for pre-Nehalem platforms.
Child sched domain should clear SD_PREFER_SIBLING if parent will have
SD_POWERSAVINGS_BALANCE because they are contradicting.

Sets the flags correctly based on sched_mc_power_savings.

Signed-off-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20100208100555.GD2931@dirshya.in.ibm.com>
Cc: stable@kernel.org [2.6.32.x]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>