Fix missing dependency declaration in test

muladd() (restartable or not) is only available when at least one short
weirstrass curve is enabled.

Found by depends.py curves (now that restartable is part of full).

Also, document that restartable only work for short weierstrass curves
(actually unrelated, but this made me think of that).

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/tests/suites/test_suite_ecp.function b/tests/suites/test_suite_ecp.function
index 7d29e52..2971c57 100644
--- a/tests/suites/test_suite_ecp.function
+++ b/tests/suites/test_suite_ecp.function
@@ -237,7 +237,7 @@
 }
 /* END_CASE */
 
-/* BEGIN_CASE depends_on:MBEDTLS_ECP_RESTARTABLE */
+/* BEGIN_CASE depends_on:MBEDTLS_ECP_RESTARTABLE:MBEDTLS_ECP_SHORT_WEIERSTRASS_ENABLED */
 void ecp_muladd_restart( int id, char *xR_str, char *yR_str,
                          char *u1_str, char *u2_str,
                          char *xQ_str, char *yQ_str,