ARM: OMAP3+: voltage: introduce omap vc / vp params for voltagedomains

These new structs will hold the sleep voltage levels (omap_vc_params)
and voltage processor min / max voltages (omap_vp_params.) Previously
these were part of the PMIC struct, but they do not really belong there,
as they are OMAP chip specific, not PMIC specific parameters. voltdm
code is also changed to use the new structs.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>