power: supply: ltc2941-battery-gauge: Add LTC2944 support

LTC2944 is compatible with LTC2943, but uses different
voltage and current computing constants.

Signed-off-by: Dragos Bogdan <dragos.bogdan@analog.com>
Signed-off-by: Ladislav Michl <ladis@linux-mips.org>
Tested-by: Dragos Bogdan <dragos.bogdan@analog.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>