changelog: add note about EC curves support removal in TLS

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/ChangeLog.d/secp256k1-removal.txt b/ChangeLog.d/secp256k1-removal.txt
new file mode 100644
index 0000000..9933b8e
--- /dev/null
+++ b/ChangeLog.d/secp256k1-removal.txt
@@ -0,0 +1,3 @@
+Removals
+   * Support for secp192k1, secp192r1, secp224k1 and secp224r1 EC curves is
+     removed from TLS.