Update qcom_defconfig to allow cpuidle for QCOM cpus.

* Enable QCOM_PM
* Enable ARM_CPUIDLE

Cc: Kumar Gala <galak@codeaurora.org>
Signed-off-by: Lina Iyer <lina.iyer@linaro.org>
Signed-off-by: Kumar Gala <galak@codeaurora.org>