power: supply: qti_battery_charger: add SSR support

Add subsystem restart (SSR) support to battery charger driver so
that it can stop read/write properties when subsystem goes down.
Also, send message to enable notification again once subsystem
comes up.

Change-Id: I64f3abfa1d12c4e6a65fd01d7f66155c8741e68a
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>