Sort out MD dependencies in RSA tests

When MD is only used to compute a size, use md_internal.h instead.

When it's actually used to compute a hash, mark the test function as
depending on it. This is probably suboptimal in the long run, and we
might want to either adapt the code so that it can use PSA Crypto
instead, or just pre-compute the hash in the test data.

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/tests/suites/test_suite_rsa.function b/tests/suites/test_suite_rsa.function
index f5f5159..dbd4b53 100644
--- a/tests/suites/test_suite_rsa.function
+++ b/tests/suites/test_suite_rsa.function
@@ -76,7 +76,7 @@
 }
 /* END_CASE */
 
-/* BEGIN_CASE */
+/* BEGIN_CASE depends_on:MBEDTLS_MD_C */
 void mbedtls_rsa_pkcs1_sign( data_t * message_str, int padding_mode,
                              int digest, int mod, int radix_P, char * input_P,
                              int radix_Q, char * input_Q, int radix_N,
@@ -131,7 +131,7 @@
 }
 /* END_CASE */
 
-/* BEGIN_CASE */
+/* BEGIN_CASE depends_on:MBEDTLS_MD_C */
 void mbedtls_rsa_pkcs1_verify( data_t * message_str, int padding_mode,
                                int digest, int mod, int radix_N,
                                char * input_N, int radix_E, char * input_E,