dt-bindings: i2c: st,stm32-i2c: Document interrupt-names property

Document interrupt-names property with "event" and "error" interrupt names.
This fixes dtbs_check warnings when building current Linux DTs:

"
arch/arm/boot/dts/stm32mp153c-dhcom-drc02.dtb: i2c@40015000: Unevaluated properties are not allowed ('interrupt-names' was unexpected)
"
Signed-off-by: Marek Vasut <marex@denx.de>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

Documentation/devicetree/bindings/i2c/st,stm32-i2c.yaml

@@ -57,6 +57,11 @@ properties:
       - description: interrupt ID for I2C event
       - description: interrupt ID for I2C error
 
+  interrupt-names:
+    items:
+      - const: event
+      - const: error
+
   resets:
     maxItems: 1