power: supply: twl4030_charger: correct comparision with old current

Driver reads existing current value from two 8-bit registers, but then
compares only one of them with the new 16-bit value.  clang W=1 is also
not happy:

  twl4030_charger.c:243:16: error: variable 'cur_reg' set but not used [-Werror,-Wunused-but-set-variable]

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240705113113.42851-2-krzysztof.kozlowski@linaro.org


Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>