qcom-common: Don't use CM PowerHAL for all targets

Change-Id: I51b0efa1f399b2679253f100dfce84f3a774e7e3
qcom-common: TARGET_POWERHAL_VARIANT = cm

 * Use this for all Samsungs by default. Individual devices can
   override if they choose.

Change-Id: Ibb1d8b695c10d32bdd314fa355c197e8248c4b1a