power: smb1390-psy: Add support for dual charge Pumps

Dual SMB1390 PMICs, master and slave, are supported as companion chargers
to the primary charge PMIC. The CP driver is split into master and slave
drivers, the slave mirrors master's operations.

The master acts as the proxy for both, interacting with main charger and
userspace, with the inherited interface and die temp of master alone is
exposed.

The Master SMB1390 handles:
- All IRQ
- Switching of slave SMB1390
- Configuring ILIM of slave

Currently, the supported mode is MID(input)-VBAT(output). When ILIM falls
below threshold ilim, both SMB are turned off. In the absence of slave
charge pump, the drivers fall back to support a single charge pump like
before, for backward compatibility.

Change-Id: I7c16d8d5e205ddc4cd212b0e7c5d2e54eea78df1
Signed-off-by: Harry Yang <harryy@codeaurora.org>
Signed-off-by: Sahil Chandna <chandna@codeaurora.org>