bq27xxx: add voltage min design for bq27000 and bq27200

bq27xxx: add voltage min design for bq27000 and bq27200

The bq27x00 gauges have an EEPROM register which contains the value of
the voltage that should be considered to be zero battery capacity. Expose
this to userspace using the VOLTAGE_MIN_DESIGN property.

Tested on Nokia N900 with bq27200.

Signed-off-by: Sicelo A. Mhlongo <absicsz@gmail.com>
Acked-by: Pali Rohár <pali@kernel.org>
Link: https://lore.kernel.org/r/20241125151321.45440-1-absicsz@gmail.com
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>