mfd: syscon: Use scoped variables with memory allocators to simplify error paths

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/20240707114823.9175-2-krzysztof.kozlowski@linaro.org


Signed-off-by: Lee Jones <lee@kernel.org>