Avoid a dependency on MD in test_suite_pk

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/tests/suites/test_suite_pk.function b/tests/suites/test_suite_pk.function
index 34ebdcc..f7ef421 100644
--- a/tests/suites/test_suite_pk.function
+++ b/tests/suites/test_suite_pk.function
@@ -7,6 +7,8 @@
 #include "mbedtls/ecp.h"
 #include "mbedtls/rsa.h"
 
+#include "md_internal.h"
+
 #include <limits.h>
 #include <stdint.h>
 
@@ -1316,8 +1318,7 @@
     size_t sig_len;
     unsigned char sig[MBEDTLS_PK_SIGNATURE_MAX_SIZE];
     unsigned char hash[MBEDTLS_MD_MAX_SIZE];
-    const mbedtls_md_info_t *md_info = mbedtls_md_info_from_type( md_alg );
-    size_t hash_len = mbedtls_md_get_size( md_info );
+    size_t hash_len = mbedtls_md_internal_get_size( md_alg );
     void const *options = NULL;
     mbedtls_pk_rsassa_pss_options rsassa_pss_options;
     memset( hash, 0x2a, sizeof( hash ) );
@@ -1338,8 +1339,8 @@
     if( key_pk_type == MBEDTLS_PK_RSASSA_PSS )
     {
         rsassa_pss_options.mgf1_hash_id = md_alg;
-        TEST_ASSERT( md_info != NULL );
-        rsassa_pss_options.expected_salt_len = mbedtls_md_get_size( md_info );
+        TEST_ASSERT( hash_len != 0 );
+        rsassa_pss_options.expected_salt_len = hash_len;
         options = (const void*) &rsassa_pss_options;
     }
     TEST_ASSERT( mbedtls_pk_verify_ext( key_pk_type, options, &pk, md_alg,