file_systems: Overlay layers only support being mounted with super volumes.

Fixes #16669.

src/add-ons/kernel/file_systems/layers/attribute_overlay/attribute_overlay.cpp

@@ -1994,6 +1994,9 @@ static status_t
 overlay_mount(fs_volume *volume, const char *device, uint32 flags,
 	const char *args, ino_t *rootID)
 {
+	if (volume->super_volume == NULL)
+		return B_UNSUPPORTED;
+
 	TRACE_VOLUME("mounting attribute overlay\n");
 	volume->private_volume = new(std::nothrow) OverlayVolume(volume);
 	if (volume->private_volume == NULL)

src/add-ons/kernel/file_systems/layers/log_overlay/log_overlay.cpp

@@ -1106,6 +1106,9 @@ static status_t
 overlay_mount(fs_volume *volume, const char *device, uint32 flags,
 	const char *args, ino_t *rootID)
 {
+	if (volume->super_volume == NULL)
+		return B_UNSUPPORTED;
+
 	char filename[256];
 	snprintf(filename, sizeof(filename), "%s%s", kLogFilePrefix, device);
 	filename[sizeof(filename) - 1] = 0;

src/add-ons/kernel/file_systems/layers/write_overlay/write_overlay.cpp

@@ -2557,6 +2557,9 @@ static status_t
 overlay_mount(fs_volume *volume, const char *device, uint32 flags,
 	const char *args, ino_t *rootID)
 {
+	if (volume->super_volume == NULL)
+		return B_UNSUPPORTED;
+
 	TRACE_VOLUME("mounting write overlay\n");
 	volume->private_volume = new(std::nothrow) OverlayVolume(volume);
 	if (volume->private_volume == NULL)