qpnp-smb2: smb-lib: add charge_done property

Currently, charging status is shown as full for both the charge
termination and inhibit cases. However, there is a need to know
when the charge termination really happens.

Add charge_done property to qpnp-smb2 driver so that the clients
can read that property to distinguish termination and inhibit.

Change-Id: If2bd750af412adf1eea7b913caed9a3eb3b763db
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>