[C] Fix bitset property encoding length function name.

Author: denizevrenci

sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/c/CGenerator.java

@@ -2227,10 +2227,11 @@ private static void generateBitsetPropertyFunctions(
  containingStructName));
 
  sb.append(String.format("\n" +
- "SBE_ONE_DEF size_t %1$s_encoding_length(void)\n" +
+ "SBE_ONE_DEF size_t %s_%s_encoding_length(void)\n" +
  "{\n" +
- " return %2$d;\n" +
+ " return %d;\n" +
  "}\n",
+ containingStructName,
  propertyName,
  token.encoding().primitiveType().size()));
  }