power: qpnp-linear-charger: fix of_property_read_bool() usage

The function of_property_read_bool() is used in the linear-charger
driver to test for the existence of non-boolean device tree properties.
These calls will work as expected; however, of_property_read_bool() is
only meant to be used for reading boolean device tree properties.

Replace the usage of of_property_read_bool() which test for
non-boolean property existence with of_find_property().

CRs-Fixed: 739482
Change-Id: I386644b619cbfc090dbf187dc241a3627afe7446
Signed-off-by: Tirupathi Reddy T <tirupath@codeaurora.org>