power: bq28400: update name of device tree properties on temperature

In current bq28400 driver implementation, name of device tree properties on
temperature are not clear about their unit. As bq28400 uses celsius degree
as the unit for temperature, update those temperature related device tree
properties with "-degc" suffix.

Change-Id: Iee9020891985abebd681b89a32057581e43ed20b
Signed-off-by: Ke Liu <keliu@codeaurora.org>