power: qpnp-smbcharger: make bpd default to no change

Currently the smbcharger driver defaults to batt_therm-based detection
when the bpd property is not set. Change it to use the preconfigured
hardware default to handle cases where that is desirable.

Change-Id: I6d52cbf6cff7ec1d04c57aaf73bb1b3b9f4c43b7
Signed-off-by: Xiaozhe Shi <xiaozhes@codeaurora.org>