Replace MBEDTLS_MD_CAN_MD5 with PSA_WANT_ALG_MD5

Signed-off-by: Elena Uziunaite <elena.uziunaite@arm.com>
diff --git a/library/x509.c b/library/x509.c
index 199c4fb..34b6a5a 100644
--- a/library/x509.c
+++ b/library/x509.c
@@ -129,7 +129,7 @@
 static inline const char *md_type_to_string(mbedtls_md_type_t md_alg)
 {
     switch (md_alg) {
-#if defined(MBEDTLS_MD_CAN_MD5)
+#if defined(PSA_WANT_ALG_MD5)
         case MBEDTLS_MD_MD5:
             return "MD5";
 #endif