Different boards benefit differently from the available
seven C-states for cpu idle. In most cases, only few,
properly spaced (in terms of consumption and latency)
C-states are required to make the power management
optimal. Hence we need a possibility to pass which
C-states are actually used for each board.

So added the valid field to cpuidle_params and added
support to 3430sdp, which uses the paramenter passing.
Signed-off-by: Kalle Jokiniemi <kalle.jokiniemi@digia.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>