power: pm8921-charger: round up vddmax adjustments

It was observed that the battery was charged at voltage less than the
max voltage. This was because the vdd max algorithm rounded down the
voltage.

Use voltage rounding up instead.

Change-Id: Ifb5e9c265b8f616e82abbb979ecfac5e6604b25d
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>