power: qpnp-vmbms: Force S2 state at boot

The VMBMS states are managed by the driver. There is
a possibility that VMBMS may continue operating in its
internal state machine if not forced to a state at boot.
Avoid this by forcing BMS into S2 at bootup.

CRs-Fixed: 828804
Change-Id: If222633c9086b38ea72485c9494aca74db2036e1
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>