Update tests/suites/test_suite_pkcs7.function

Address test dependency issue

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/tests/suites/test_suite_pkcs7.function b/tests/suites/test_suite_pkcs7.function
index a1de999..14a0882 100644
--- a/tests/suites/test_suite_pkcs7.function
+++ b/tests/suites/test_suite_pkcs7.function
@@ -10,7 +10,7 @@
 /* END_HEADER */
 
 /* BEGIN_DEPENDENCIES
- * depends_on:MBEDTLS_PKCS7_C
+ * depends_on:MBEDTLS_PKCS7_C:MBEDTLS_RSA_C
  * END_DEPENDENCIES
  */