power: Add ARC power states and update sample

Add Low Power States support to the power shim layer
and show the usage in the quark_se sample.

States are defined as follow:
- SYS_POWER_STATE_CPU_LPS: SS2 with LPSS enabled
- SYS_POWER_STATE_CPU_LPS_1: SS2 with LPSS disabled
- SYS_POWER_STATE_CPU_LPS_2: SS1 with LPSS disabled

Jira: ZEP-994

Change-Id: Ie4b93f6e539cb53fc035be00280b66b2cb0d9fea
Signed-off-by: Julien Delayen <julien.delayen@intel.com>