dt-bindings: sbrmi: Add SB-RMI hwmon driver bindings

- Document device tree bindings for AMD SB-RMI emulated service.

Signed-off-by: Akshay Gupta <Akshay.Gupta@amd.com>
Signed-off-by: Naveen Krishna Chatradhi <nchatrad@amd.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210726133615.9709-3-nchatrad@amd.com


Signed-off-by: Guenter Roeck <linux@roeck-us.net>