of: batterydata: fix a typo on flat-ocv-threshold-uv property reading

This typo cause flat_ocv_threshold_uv value can't be read correctly,
and make adjust_soc() assign a wrong value to correction_limit_uv in
bms driver.

Change-Id: Ifc00c63070281e3adfafd3f10559f2660644af90
Signed-off-by: Wu Fenglin <fenglinw@codeaurora.org>