power: qpnp-charger: force on VREF_BAT_THM

The VREF_BAT_THM rail can cause the SMBB
peripheral to incorrectly report the battery
is overheating (0V).

Fix this by always forcing on VREF_BAT_THM
to make sure BAT_THM is not pulled low.

Change-Id: I863b126d003508e16d8a2822de11f3074e3a4c8c
Signed-off-by: David Keitel <dkeitel@codeaurora.org>