power: smb135x-charger: initialize wakeup source for parallel charger

The charger driver holds a wake source for every i2c read/write operation
initialize wakeup source in parallel charger probe.

CRs-Fixed: 1052761
Change-Id: I16a842457a370dc73659207bb9b935d6bd7d688b
Signed-off-by: Ashay Jaiswal <ashayj@codeaurora.org>