power: smb5: Fix usb input current reporting

For PMI632, the scaling factor of USB input current channel is
different from that of PM8150B and PM6150 due to which incorrect
usb input current is getting reported. Add support to select the
ADC channel scaling factor based on PMI type to fix this.

Change-Id: I610ec44aa24cb3a83ac2bf886f3210d06d94f72a
Signed-off-by: Umang Agrawal <uagrawal@codeaurora.org>