Minor documentation improvements

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/include/mbedtls/ecp.h b/include/mbedtls/ecp.h
index b317d70..980ec5e 100644
--- a/include/mbedtls/ecp.h
+++ b/include/mbedtls/ecp.h
@@ -97,7 +97,7 @@
 /* Note: when adding a new curve:
  * - Add it at the end of this enum, otherwise you'll break the ABI by
  *   changing the numerical value for existing curves.
- * - Increment MBEDTLS_ECP_DP_MAX below.
+ * - Increment MBEDTLS_ECP_DP_MAX below if needed.
  * - Add the corresponding MBEDTLS_ECP_DP_xxx_ENABLED macro definition to
  *   config.h.
  * - List the curve as a dependency of MBEDTLS_ECP_C and