power: smb138x: enable interrupt sources for usb-src-change irq

By default, usb-src-change irq will not be triggered because none of
the interrupt sources is enabled.

Enable APSD completion, HVDCP detection, authentication and adapter
voltage change as irq sources.

This is needed for smb138x as standalone charger.

Change-Id: If8bed10b25f03695aeca3a6083772b75ceff3f96
Signed-off-by: Harry Yang <harryy@codeaurora.org>