max8925_power: Do not read random data from chip registers

Reading the voltage, charge etc requires that we tell the chip
what property we want to read before reading it according to
maxim.

Signed-off-by: Philip Rakity <prakity@marvell.com>
Signed-off-by: Thomas Liu <Thomas.Liu@maxim-ic.com>
Tested-by: Ted Bennett <tbennett@marvell.com>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>