pldm: Removing default string length

Removing default string length from BIOS json configuration
files.

String BIOS attributes defined in BIOS configuration json file
contains "default_string_length". Providing default string length
manually is error prone. As String length can be calculated and
populated easily in the code, removing json support for
default_string_length.

Tested: Power on/off
        Gtests passed.

Change-Id: I7604d8ccedd60a39ba07e1df67ff5712f31e7f6e
Signed-off-by: Archana Kakani <archana.kakani@ibm.com>
diff --git a/libpldmresponder/bios_string_attribute.cpp b/libpldmresponder/bios_string_attribute.cpp
index d52cdc4..d55c99a 100644
--- a/libpldmresponder/bios_string_attribute.cpp
+++ b/libpldmresponder/bios_string_attribute.cpp
@@ -33,8 +33,9 @@
 
     stringInfo.minLength = entry.at("minimum_string_length");
     stringInfo.maxLength = entry.at("maximum_string_length");
-    stringInfo.defLength = entry.at("default_string_length");
     stringInfo.defString = entry.at("default_string");
+    stringInfo.defLength =
+        static_cast<uint16_t>((stringInfo.defString).length());
 
     pldm_bios_table_attr_entry_string_info info = {
         0,