bios: fix bugs in PLDM BIOS

1. Correct json file example for enum type.
2. Enhance conditions for getBIOSAttributeValueTable.

Change-Id: Iba99a2aa0315623baeedec30170739030a6ebb4c
Signed-off-by: Carol Wang <wangkair@cn.ibm.com>
diff --git a/libpldmresponder/bios.cpp b/libpldmresponder/bios.cpp
index 4372e21..e0ded59 100644
--- a/libpldmresponder/bios.cpp
+++ b/libpldmresponder/bios.cpp
@@ -765,7 +765,7 @@
                 }
                 break;
             case PLDM_BIOS_ATTR_VAL_TABLE:
-                if (BIOSAttributeTable.isEmpty())
+                if (BIOSAttributeTable.isEmpty() || BIOSStringTable.isEmpty())
                 {
                     rc = PLDM_BIOS_TABLE_UNAVAILABLE;
                 }
diff --git a/libpldmresponder/examples/bios/enum_attrs.json b/libpldmresponder/examples/bios/enum_attrs.json
index 01f8526..0b2c212 100644
--- a/libpldmresponder/examples/bios/enum_attrs.json
+++ b/libpldmresponder/examples/bios/enum_attrs.json
@@ -5,15 +5,15 @@
          "attribute_name" : "HMCManagedState",
          "possible_values" : [ "On", "Off" ],
          "default_values" : [ "On" ],
-         "object_path" : "/xyz/abc/def",
-         // This BIOS attribute has a D-Bus property as backend. 
+         # This BIOS attribute has a D-Bus property as backend.
          "dbus":
             {
+               "object_path" : "/xyz/abc/def",
                "interface" : "xyz.openbmc_project.HMCManaged.State",
                "property_name" : "State",
                "property_type" : "string",
                # Number of property_values should match to the number of possible values.
-               # Each is entry in the possible_values is mapped to entry in property_values. 
+               # Each is entry in the possible_values is mapped to entry in property_values.
                "property_values" : ["xyz.openbmc_project.State.On", "xyz.openbmc_project.State.Off"]
             }
       },