power: supply: smblite: Only enable temp change IRQ when VBUS present

Charger die temperature monitoring in hardware will be always enabled
even when charger is absent. This helps flash driver to detect charger
die temperature status and set flash current correctly. In this case,
to avoid charger driver receiving unrelated charger die temperature
change interrupt, only enable this IRQ when charger is inserted.

Change-Id: I1a3e86a420df4015d3f3a6a888d45c5fdd46f54b
Signed-off-by: Fenglin Wu <fenglinw@codeaurora.org>