Fix cpufreq for imx8mq

* Removes hard-coded min/max, relies on DT values.
* "arm" regulator doesn't exist, rename dc-supply to arm-supply so that
arm properly resolves. This matches imx8mm DT.

Tested:
* Force performance/powersave, verify regulator voltage change.

Change-Id: Id7598578b357d77a5c0dfbd1b246458e964f1ed3
2 files changed