Provide and use internal function mbedtls_zeroize_and_free()

Signed-off-by: Tom Cosgrove <tom.cosgrove@arm.com>
diff --git a/library/x509_crl.c b/library/x509_crl.c
index f644203..79ace8f 100644
--- a/library/x509_crl.c
+++ b/library/x509_crl.c
@@ -587,8 +587,7 @@
 
     ret = mbedtls_x509_crl_parse(chain, buf, n);
 
-    mbedtls_platform_zeroize(buf, n);
-    mbedtls_free(buf);
+    mbedtls_zeroize_and_free(buf, n);
 
     return ret;
 }
@@ -704,14 +703,12 @@
         while (entry_cur != NULL) {
             entry_prv = entry_cur;
             entry_cur = entry_cur->next;
-            mbedtls_platform_zeroize(entry_prv,
+            mbedtls_zeroize_and_free(entry_prv,
                                      sizeof(mbedtls_x509_crl_entry));
-            mbedtls_free(entry_prv);
         }
 
         if (crl_cur->raw.p != NULL) {
-            mbedtls_platform_zeroize(crl_cur->raw.p, crl_cur->raw.len);
-            mbedtls_free(crl_cur->raw.p);
+            mbedtls_zeroize_and_free(crl_cur->raw.p, crl_cur->raw.len);
         }
 
         crl_prv = crl_cur;