power_supply: max17040: Use system efficient workqueues

The scheduled work in max17040_battery driver reads device parameters
and stores them in memory. Any CPU could do that so use system efficient
workqueues to limit unnecessary CPU wake ups.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>