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/libpldm/bios_table.c b/libpldm/bios_table.c
index 8c04f36..4af4661 100644
--- a/libpldm/bios_table.c
+++ b/libpldm/bios_table.c
@@ -625,7 +625,7 @@
 
 void pldm_bios_table_attr_value_entry_encode_enum(
     void *entry, size_t entry_length, uint16_t attr_handle, uint8_t attr_type,
-    uint8_t count, uint8_t *handles)
+    uint8_t count, const uint8_t *handles)
 {
 	size_t length =
 	    pldm_bios_table_attr_value_entry_encode_enum_length(count);