hammerhead: Use CM power HAL

Using the qcom power HAL, the proprietary mpdecision and CM
causes the first two cores to get locked at relatively high
frequencies (1.2 and/or 1.4 GHz).

To see the problem, boot the phone and then open Settings >>
Performance and you'll likely see the minimum speed > 1 GHz.
If you leave the phone connected to a charger and otherwise
idle and then check the time-in-state stats, you'll see it is
entirely above 1 GHz.  Given an idle phone that can't sleep,
I would expect it to be most at 300 MHz.

Using the CM power HAL fixes this problem.

Change-Id: Ice2643a91dc4d864fd0ed5970f9ee8521dce4182
Revert "hammerhead: Remove the maxcpus arg"

This reverts commit 16a1c8e81a45b02ef4d468c72a7ccaec297d61ff.