power: qpnp-bms: add a taper charging notification

SMB chip only has a 20-30mV accuracy for VDDMAX. Since it never
meets the 10mV accuracy that BMS expects, taper charging detection
will fail. Fix this by implementing the notification from SMB
driver to BMS driver.

Change-Id: I1936aecec2c281dc98173b80db105871e6869a1d
Signed-off-by: Zhenhua Huang <zhenhuah@codeaurora.org>