dt-bindings: trivial-devices: Add compatible string synaptics,synaptics_i2c

Add compatible string synaptics,synaptics_i2c for synaptics touch pad. It
match existed driver drivers/input/mouse/synaptics_i2c.c.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>

Documentation/devicetree/bindings/trivial-devices.yaml

@@ -395,6 +395,8 @@ properties:
           - sparkfun,qwiic-joystick
             # Sierra Wireless mangOH Green SPI IoT interface
           - swir,mangoh-iotport-spi
+            # Synaptics I2C touchpad
+          - synaptics,synaptics_i2c
             # Ambient Light Sensor with SMBUS/Two Wire Serial Interface
           - taos,tsl2550
             # Digital PWM System Controller PMBus

Documentation/devicetree/bindings/vendor-prefixes.yaml

@@ -1552,6 +1552,9 @@ patternProperties:
     description: Sierra Wireless
   "^syna,.*":
     description: Synaptics Inc.
+  "^synaptics,.*":
+    description: Synaptics Inc.
+    deprecated: true
   "^synology,.*":
     description: Synology, Inc.
   "^synopsys,.*":