Bump version to Mbed TLS 2.22.0

Signed-off-by: Janos Follath <janos.follath@arm.com>
diff --git a/ChangeLog b/ChangeLog
index a6983a7..509c74c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,6 +1,6 @@
 mbed TLS ChangeLog (Sorted per branch, date)
 
-= mbed TLS x.x.x branch released xxxx-xx-xx
+= mbed TLS 2.22.0 branch released 2020-04-14
 
 New deprecations
    * Deprecate MBEDTLS_SSL_HW_RECORD_ACCEL that enables function hooks in the