library: add remaining changes for the new ECP_LIGHT symbol

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index fccac85..d7c47e6 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -1553,10 +1553,10 @@
 
 MBEDTLS_CHECK_RETURN_CRITICAL
 int mbedtls_ssl_check_curve_tls_id(const mbedtls_ssl_context *ssl, uint16_t tls_id);
-#if defined(MBEDTLS_ECP_C)
+#if defined(MBEDTLS_ECP_LIGHT)
 MBEDTLS_CHECK_RETURN_CRITICAL
 int mbedtls_ssl_check_curve(const mbedtls_ssl_context *ssl, mbedtls_ecp_group_id grp_id);
-#endif
+#endif /* MBEDTLS_ECP_LIGHT */
 
 /**
  * \brief Return PSA EC info for the specified TLS ID.