dt-bindings: extcon: bindings for SM5703

This patch adds device-tree bindings for Silicon Mitus SM5703 MUIC.

Signed-off-by: Markuss Broks <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Chanwoo Choi <[e-mail]>

Documentation/devicetree/bindings/extcon/siliconmitus,sm5502-muic.yaml

···
     enum:
       - siliconmitus,sm5502-muic
       - siliconmitus,sm5504-muic
+      - siliconmitus,sm5703-muic
 
   reg:
     maxItems: 1
-    description: I2C slave address of the device. Usually 0x25 for SM5502,
-      0x14 for SM5504.
+    description: I2C slave address of the device. Usually 0x25 for SM5502
+      and SM5703, 0x14 for SM5504.
 
   interrupts:
     maxItems: 1