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.h b/libpldm/bios_table.h
index d0e06a4..66d620f 100644
--- a/libpldm/bios_table.h
+++ b/libpldm/bios_table.h
@@ -509,7 +509,7 @@
  */
 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 *handle_indexes);
+    uint8_t count, const uint8_t *handle_indexes);
 
 /** @brief Get number of current values for the enum entry
  *  @param[in] entry - Pointer to bios attribute value table entry