max17042_battery: Fix missing verify_model_lock() return value check

The second error check is unreachable because the lock function isn't
assigned to ret.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Acked-by: Ramakrishna Pallala <ramakrishna.pallala@intel.com>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>