hwmon: qpnp-adc: Add scaling support for Die temp channel

The voltage measured by the HKADC is related to the junction
temperature and scaled by the following equation :-
Voltage = 1.4825 – 0.0033*Temp

Change-Id: I47812869208a9d34f38137d23693acd7446907d1
Signed-off-by: Jishnu Prakash <jprakash@codeaurora.org>
Signed-off-by: Nicholas Troast <ntroast@codeaurora.org>