bios: Implement BIOSEnumAttribute

Implement BIOSEnumAttribute, most of the code is copied from
bios/bios_parser.cpp.

Implement SetAttrValueOnDbus and constructEntry for enum attribute

Signed-off-by: John Wang <wangzqbj@inspur.com>
Change-Id: Ia6230485fd2d6d05f9f2ddb3a80b81f6556aee9f
diff --git a/test/mocked_bios.hpp b/test/mocked_bios.hpp
index eb95c33..568fad9 100644
--- a/test/mocked_bios.hpp
+++ b/test/mocked_bios.hpp
@@ -14,6 +14,8 @@
     }
 
     MOCK_METHOD(uint16_t, findHandle, (const std::string&), (const override));
+
+    MOCK_METHOD(std::string, findString, (const uint16_t), (const override));
 };
 
 void checkHeader(const Table& attrEntry, const Table& attrValueEntry)