power: smb1360: Store the initial IRQ status register value

There is a possibility that an IRQ status change may not
registered if the IRQ status value (prev_val) is not updated
while reading the initial state. Make sure that the IRQ
status is updated in the irq handler structure.

CRs-Fixed: 783017
Change-Id: Ifcffb7b31f84f197eb73c7a80fafbada98f93cc0
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>