dt-bindings: arm: samsung: Add compatible string for the Galaxy S2

Add compatible string for the Samsung Galaxy S2 (GT-I9100 version), which
is an Exynos4210 based device.
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>

Documentation/devicetree/bindings/arm/samsung/samsung-boards.yaml

@@ -52,6 +52,7 @@ properties:
         items:
           - enum:
               - insignal,origen                 # Insignal Origen
+              - samsung,i9100                   # Samsung Galaxy S2 (GT-I9100)
               - samsung,smdkv310                # Samsung SMDKV310 eval
               - samsung,trats                   # Samsung Tizen Reference
               - samsung,universal_c210          # Samsung C210