regulator: qpnp-oledb: Add support for LAB_VREG_NOT_OK notifier

Register a notifier callback for LAB_VREG_NOT_OK, which is triggered
by the LABIBB driver when short circuit(SC) is detected on the LAB
rail. Disable the OLEDB module upon receiving the LAB_VREG_NOT_OK
notification.

Change-Id: Ia3cc19d9a3c2f32acc413677a9ea4b3100464cd2
Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>