drm/vc4: hdmi: Use debugfs private field

We're calling vc4_debugfs_add_file with our struct vc4_hdmi pointer set
in the private field, but we don't use that field and go through the
main struct vc4_dev to get it.

Let's use the private field directly, that will save us some trouble
later on.
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Tested-by: Chanwoo Choi <cw00.choi@samsung.com>
Tested-by: Hoegeun Kwon <hoegeun.kwon@samsung.com>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/24028dc06c379dbc71f98e027cce2839fdd446ce.1599120059.git-series.maxime@cerno.tech

drivers/gpu/drm/vc4/vc4_hdmi.c

@@ -183,9 +183,7 @@ static const struct debugfs_reg32 hd_regs[] = {
 static int vc4_hdmi_debugfs_regs(struct seq_file *m, void *unused)
 {
 	struct drm_info_node *node = (struct drm_info_node *)m->private;
-	struct drm_device *dev = node->minor->dev;
-	struct vc4_dev *vc4 = to_vc4_dev(dev);
-	struct vc4_hdmi *hdmi = vc4->hdmi;
+	struct vc4_hdmi *hdmi = node->info_ent->data;
 	struct drm_printer p = drm_seq_file_printer(m);
 
 	drm_print_regset32(&p, &hdmi->hdmi_regset);