Add ChangeLog entry

Signed-off-by: Thomas Daubney <thomas.daubney@arm.com>
diff --git a/ChangeLog.d/remove_ssl_session_compression.txt b/ChangeLog.d/remove_ssl_session_compression.txt
new file mode 100644
index 0000000..dc59f1c
--- /dev/null
+++ b/ChangeLog.d/remove_ssl_session_compression.txt
@@ -0,0 +1,5 @@
+Removals
+   * Remove compression property from SSL session struct.
+     MBEDTLS_SSL_COMPRESS_NULL is now the only supported
+     compression option and can be used for compatibility
+     reasons. Changes requested in #4223.