Changelog entry for MBEDTLS_ECP_MAX_BITS automatic determination

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/ChangeLog.d/ecp_max_bits.txt b/ChangeLog.d/ecp_max_bits.txt
new file mode 100644
index 0000000..b952469
--- /dev/null
+++ b/ChangeLog.d/ecp_max_bits.txt
@@ -0,0 +1,3 @@
+Removals
+   * MBEDTLS_ECP_MAX_BITS is no longer a configuration option because it is
+     now determined automatically based on supported curves.