msm: defconfig: Enable CONFIG_CPUIDLE_MULTIPLE_DRIVERS

MSM8939 device has CPUs with different latencies. Enable
CONFIG_CPUIDLE_MULTIPLE_DRIVERS config to allow cpuidle
framework to use different drivers for different CPUs.

Change-Id: Ib4385602ce54abf149790fe5cb1e3f642957560e
Signed-off-by: Murali Nalajala <mnalajal@codeaurora.org>