Generate *Sp methods for Props

Summary:
According to #281 discussion, I introduce this as a quick fix.
It can be resolved in the future with a more appropriate solution.
Closes #282

Differential Revision: D6425388

Pulled By: IanChilds

fbshipit-source-id: c04a1333dbb14062c0465f705bf74a00bf7be9b1

litho-processor/src/main/java/com/facebook/litho/specmodels/generator/BuilderGenerator.java

@@ -418,6 +418,7 @@ static TypeSpecDataHolder generatePropsBuilderMethods(
                 ? "(float) resolveDimenSize"
                 : "resolveDimenSize";
         dataHolder.addTypeSpecDataHolder(pxBuilders(specModel, prop, requiredIndex));
+        dataHolder.addTypeSpecDataHolder(sipBuilders(specModel, prop, requiredIndex));
         dataHolder.addTypeSpecDataHolder(
             resBuilders(specModel, prop, requiredIndex, ClassNames.DIMEN_RES, offsetResolverName));
         dataHolder.addTypeSpecDataHolder(