power: smb350: Remove voltage-now property

The float voltage is not the on-line measured voltage.
When the battery voltage reaches the pre-defined float voltage,
the fast-charge current starts diminishing.

Change-Id: Ib3d4a9e33e306a1481b770b0c12667f223590e24
Signed-off-by: Amir Samuelov <amirs@codeaurora.org>