meta-ibm: Remove Power.Cap hardcoded range

The powercap range is currently hardcoded by mrw-override-settings.yaml
This commit will remove the hardcoded range and allow the full range of
values to be set.
The actual limits are available via dbus which can be used to validate
the user power cap.

Change-Id: I71e6009d5bc288c0d8480db26ce9e6782bdbd167
Signed-off-by: Chris Cain <cjcain@us.ibm.com>