Fix typo

Fix typo in ChangeLog entry.
diff --git a/ChangeLog b/ChangeLog
index 5e00c0e..81dca1a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -22,7 +22,7 @@
 Changes
    * Change the shebang line in Perl scripts to look up perl in the PATH.
      Contributed by fbrosson.
-   * Fix efailure in hmac_drbg in the benchmark sample application, when
+   * Fix failure in hmac_drbg in the benchmark sample application, when
      MBEDTLS_THREADING_C is defined. Found by TrinityTonic, #1095
 
 = mbed TLS 2.11.0 branch released 2018-06-18