OMAP3: PM: CPUidle: Start C-state definitions from base 0

The current definition of C-states starts from base 1.
Whereas, the cpuidle driver uses base 0. This patch
eliminates need for explicit mapping (add/ sbutract)
due to different base values.

Signed-off-by: Sanjeev Premi <premi@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>