power: supply: core: simplify with cleanup.h

Allocate the memory with scoped/cleanup.h to reduce error handling and
make the code a bit simpler.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240705113113.42851-1-krzysztof.kozlowski@linaro.org


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