power: supply: Fix the simple battery property names

Commit c08b1f45 ("power: supply: core: Add power_supply_battery_info
and API") introduced code to parse the simple-battery node and express
battery charging constraints. However, it parsed that node using the
properties constant_charge_current_max_microamp and
constant_charge_voltage_max_microvolt, while the device tree binding for
the simple-battery node uses dashes to separate the words in those
properties (constant-charge-current-max-microamp and
constant-charge-voltage-max-microvolt).

Let's make the code match the binding.

Fixes: c08b1f45 ("power: supply: core: Add power_supply_battery_info and API")
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>