msm: defconfig: Enable CONFIG_CPUIDLE_MULTIPLE_DRIVERS

MSM8994 device has cpus with different properties. Enable above mentioned
config to ensure that cpuidle driver initializes accordingly.

Change-Id: Ibffb6e51bda54a9756204d0a864eb1e80efa6b69
Signed-off-by: Mahesh Sivasubramanian <msivasub@codeaurora.org>