dt-bindings: trivial-devices: Document ABB sensors

Add documentation for spi based ABB sensors, which are
currently operated from userspace.

Signed-off-by: Heiko Schocher <hs@denx.de>
Link: https://patch.msgid.link/20250719063355.73111-2-hs@denx.de
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: hsdenx

Documentation/devicetree/bindings/trivial-devices.yaml

@@ -30,6 +30,8 @@ properties:
     items:
       # Entries are sorted alphanumerically by the compatible
       - enum:
+            # ABB register based spi sensors
+          - abb,spi-sensor
             # Acbel fsg032 power supply
           - acbel,fsg032
             # SMBus/I2C Digital Temperature Sensor in 6-Pin SOT with SMBus Alert and Over Temperature Pin