power: supply: smb1390: Add support to make SMB1390 driver GKI compliant

Add support for charge pump master and slave power supplies through IIO
devices and properties under them through IIO channels under the device.

Change-Id: I60e4ae948401ce006c731c5cc09334b7aee7ce07
Signed-off-by: Jishnu Prakash <jprakash@codeaurora.org>
Signed-off-by: Ashish Chavan <ashichav@codeaurora.org>