power: qpnp-fg-gen3: add support to register with thermal core framework

Add support to register FG driver to register with thermal core
framework so that the battery temperature can be monitored by any
thermal governor and userspace is one of them.

Change-Id: Ia7e491b249e688c7b5d84b13caf1d390d24714b1
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>