Adapt tests to work on all possible minimum RSA key sizes

Signed-off-by: Waleed Elmelegy <waleed.elmelegy@arm.com>
diff --git a/tests/suites/test_suite_pk.function b/tests/suites/test_suite_pk.function
index bbcad93..3ea9e3d 100644
--- a/tests/suites/test_suite_pk.function
+++ b/tests/suites/test_suite_pk.function
@@ -21,8 +21,8 @@
 /* Used for properly sizing the key buffer in pk_genkey_ec() */
 #include "psa_util_internal.h"
 
-#define RSA_KEY_SIZE 1024
-#define RSA_KEY_LEN   128
+#define RSA_KEY_SIZE   MBEDTLS_RSA_MIN_KEY_SIZE
+#define RSA_KEY_LEN   (MBEDTLS_RSA_MIN_KEY_SIZE/8)
 
 #if defined(MBEDTLS_PK_USE_PSA_EC_DATA)
 static int pk_genkey_ec(mbedtls_pk_context *pk, mbedtls_ecp_group_id grp_id)