power: pm8921-charger: use resume_voltage_delta

Since the driver will be changing the max vdd if the battery
temperature enters warm or cool zone, it should also change
the vbatdet voltage so resume of charging can begin accordingly.

Also provide a means to quickly debug is the battery is in cool/warm
zone.

Change-Id: I0fe83a4fabf76711bf86377c3ac23cceecb6e98b
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>