power: supply: max17040: Correct voltage reading

According to the datasheet available at (1), the bottom four
bits are always zero and the actual voltage is 1.25x this value
in mV.  Since the kernel API specifies that voltages should be in
uV, it should report 1250x the shifted value.

1) https://datasheets.maximintegrated.com/en/ds/MAX17040-MAX17041.pdf



Signed-off-by: Jonathan Bakker <xc-racer2@live.ca>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>