test: fix dependencies in DER and PEM tests

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/tests/suites/test_suite_pkwrite.function b/tests/suites/test_suite_pkwrite.function
index a304e07..11bc5a8 100644
--- a/tests/suites/test_suite_pkwrite.function
+++ b/tests/suites/test_suite_pkwrite.function
@@ -30,7 +30,11 @@
         if (is_der) {
             ret = mbedtls_pk_write_pubkey_der(&key, buf, check_buf_len);
         } else {
+#if defined(MBEDTLS_PEM_WRITE_C)
             ret = mbedtls_pk_write_pubkey_pem(&key, buf, check_buf_len);
+#else
+            ret = MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE;
+#endif
         }
     } else {
         TEST_EQUAL(mbedtls_pk_parse_keyfile(&key, key_file, NULL,
@@ -38,7 +42,11 @@
         if (is_der) {
             ret = mbedtls_pk_write_key_der(&key, buf, check_buf_len);
         } else {
+#if defined(MBEDTLS_PEM_WRITE_C)
             ret = mbedtls_pk_write_key_pem(&key, buf, check_buf_len);
+#else
+            ret = MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE;
+#endif
         }
     }
 
@@ -66,7 +74,7 @@
  * END_DEPENDENCIES
  */
 
-/* BEGIN_CASE depends_on:MBEDTLS_PEM_WRITE_C */
+/* BEGIN_CASE */
 void pk_write_pubkey_check(char *key_file, int is_der)
 {
     pk_write_check_common(key_file, 1, is_der);
@@ -74,7 +82,7 @@
 }
 /* END_CASE */
 
-/* BEGIN_CASE depends_on:MBEDTLS_PEM_WRITE_C */
+/* BEGIN_CASE */
 void pk_write_key_check(char *key_file, int is_der)
 {
     pk_write_check_common(key_file, 0, is_der);