Corrects documentation issues

Commit corrects incorrect docs in
ecdh.h and config.h.

Signed-off-by: Thomas Daubney <thomas.daubney@arm.com>
diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index c6882db..7916587 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -779,8 +779,7 @@
  *
  * \note  This option only works with the default software implementation of
  *        elliptic curve functionality. It is incompatible with
- *        MBEDTLS_ECP_ALT, MBEDTLS_ECDH_XXX_ALT, MBEDTLS_ECDSA_XXX_ALT
- *        and MBEDTLS_ECDH_LEGACY_CONTEXT.
+ *        MBEDTLS_ECP_ALT, MBEDTLS_ECDH_XXX_ALT, MBEDTLS_ECDSA_XXX_ALT.
  */
 //#define MBEDTLS_ECP_RESTARTABLE
 
diff --git a/include/mbedtls/ecdh.h b/include/mbedtls/ecdh.h
index e5edb46..765ac5e 100644
--- a/include/mbedtls/ecdh.h
+++ b/include/mbedtls/ecdh.h
@@ -51,9 +51,6 @@
  * will support alternative implementations of ECDH operations.
  * The new format is incompatible with applications that access
  * context fields directly and with restartable ECP operations.
- *
- * This option has no effect if #MBEDTLS_ECDH_C is not enabled.
- *
  */
 
 #if defined(MBEDTLS_ECP_RESTARTABLE)