extcon: add support for Samsung S2M series PMIC extcon devices

Add a driver for MUIC devices found in certain Samsung S2M series PMICs
These are USB port accessory detectors. These devices report multiple
cable states depending on the ID-GND resistance measured by an internal
ADC.

The driver includes initial support for the S2MU005 PMIC extcon.

Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>