ARM: OMAP3+: PM: VP: use uV for max and min voltage limits

Every PMIC has it's own eccentricities, For example, one of the
PMIC has MSB set to 1 for a specific function - voltage enable!
using an hardcoded value specific for TWL when copied over to
such an implementation causes the system to crash as the MSB bit
was 0 and the voltage got disabled!.

Instead we use actual values and depend on the convertion routines
to abstract out the eccentricities of each PMIC.

With this, we can now move the voltages to a common location in
voltage.h as they are no longer dependent on PMICs and expect the
PMIC's conversion routines to set a cap if the voltage is out of
reach for the PMIC.

Reported-by: Jon Hunter <jon-hunter@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Vishwanath BS <vishwanath.bs@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>