Fixed internal flash filesystem stub build issue

Internal filesystem stubs is used when both INTERNAL_FLASH_FILESYSTEM,
DISABLE_FILESYSTEM are set.

supervisor/stub/filesystem.c

@@ -31,6 +31,11 @@ void filesystem_background(void) {
     return;
 }
 
+void filesystem_tick(void)
+{
+    return;
+}
+
 bool filesystem_init(bool create_allowed, bool force_create) {
     (void)create_allowed;
     (void)force_create;

supervisor/stub/internal_flash.c

@@ -23,7 +23,7 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
-#include "supervisor/internal_flash.h"
+#include "supervisor/flash.h"
 
 #include <stdint.h>
 #include <string.h>
@@ -46,21 +46,24 @@ uint32_t supervisor_flash_get_block_count(void) {
     return 0;
 }
 
-void port_internal_flash_flush(void) {
-    return;
-}
-
 mp_uint_t supervisor_flash_read_blocks(uint8_t *dest, uint32_t block, uint32_t num_blocks) {
     return 0; // success
 }
 
-bool supervisor_flash_write_block(const uint8_t *src, uint32_t block) {
-    return true;
-}
-
 mp_uint_t supervisor_flash_write_blocks(const uint8_t *src, uint32_t block_num, uint32_t num_blocks) {
     return 0; // success
 }
 
+#if (0)
+void supervisor_flash_init_vfs(struct _fs_user_mount_t *vfs)
+{
+    return;
+}
+#endif
+
+void port_internal_flash_flush(void) {
+    return;
+}
+
 void supervisor_flash_release_cache(void) {
 }