power: power_supply: Add Wipower charger type

Add support to specify Wipower charger type. Wipower is a wireless
charging technology which uses bluetooth low energy communication
for exchanging charging parameters and can charge multiple devices
simultaneously within a single charge area.

Change-Id: I265c9db31b76b5244f4616513c95f13c578cdbf4
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>