power: power_supply: Add USB_PARALLEL charger type

Add definitions for usb parallel charger type. This charger assists
the main charging path by splitting the current drawn from the usb
charger. This reduces the current flowing through the main charging
path thereby reducing thermal impact and size of the inductor.

Change-Id: I13ffa386c234387ec057d27f35818527c2c4fcdd
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>