Remove meaningless checks decoding DB2 principals

Commit e3d9f03 (ticket 8481) added
several checks for negative length values when decoding DB2 principal
entries, including two unnecessary checks on unsigned values.  Remove
those checks as they can generate warnings.

ticket: 8491 (new)
target_version: 1.14-next
target_version: 1.13-next
tags: pullup

src/plugins/kdb/db2/kdb_xdr.c

@@ -364,8 +364,7 @@ krb5_decode_princ_entry(krb5_context context, krb5_data *content,
         krb5_kdb_decode_int16(nextloc, (*tl_data)->tl_data_length);
         nextloc += 2;
 
-        if ((*tl_data)->tl_data_length < 0 ||
-            (*tl_data)->tl_data_length > sizeleft) {
+        if ((*tl_data)->tl_data_length > sizeleft) {
             retval = KRB5_KDB_TRUNCATED_RECORD;
             goto error_out;
         }
@@ -414,8 +413,7 @@ krb5_decode_princ_entry(krb5_context context, krb5_data *content,
                 krb5_kdb_decode_int16(nextloc, key_data->key_data_length[j]);
                 nextloc += 2;
 
-                if (key_data->key_data_length[j] < 0 ||
-                    key_data->key_data_length[j] > sizeleft) {
+                if (key_data->key_data_length[j] > sizeleft) {
                     retval = KRB5_KDB_TRUNCATED_RECORD;
                     goto error_out;
                 }