power: supply: cpcap-charger: Fix charger voltages based on ADC values

With the ADC driver working, we can now fix the voltage table based on
the values read from the ADC.

Note that unlike the ICHRG registers, the VCHRG register bits don't
match the MC13783UG.pdf.

Cc: Marcel Partap <mpartap@gmx.net>
Cc: Michael Scott <michael.scott@linaro.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>