OMAP: PM: CPUfreq: obey min/max settings of policy

Use the min/max settings from CPUfreq policy rather than
processor defined min/max settings.

Without this patch, it's possible to scale frequency outside
the current policy range.

Signed-off-by: Eero Nurkkala <ext-eero.nurkkala@nokia.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>