drm/panel: boe-th101mb31ig002-28a: Fix compilation build

Commit 77dcbce63779 ("panel/th101mb31ig002-28a: Use refcounted
allocation in place of devm_kzalloc()") switched from a kmalloc +
drm_panel_init call to a devm_drm_panel_alloc one.

However, the variable it was storing the allocated pointer in doesn't
exist, resulting in a compilation breakage.

Fixes: 77dcbce63779 ("panel/th101mb31ig002-28a: Use refcounted allocation in place of devm_kzalloc()")
Signed-off-by: Maxime Ripard <[e-mail]>
Reviewed-by: Thomas Zimmermann <[e-mail]>
Tested-by: Thomas Zimmermann <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Dmitry Baryshkov <[e-mail]>

drivers/gpu/drm/panel/panel-boe-th101mb31ig002-28a.c

···
 	const struct panel_desc *desc;
 	int ret;
 
-	panel = devm_drm_panel_alloc(dev, struct panel_desc, panel,
-				     &boe_th101mb31ig002_funcs,
-				     DRM_MODE_CONNECTOR_DSI);
-	if (IS_ERR(panel))
-		return PTR_ERR(panel);
+	ctx = devm_drm_panel_alloc(&dsi->dev, struct boe_th101mb31ig002, panel,
+				   &boe_th101mb31ig002_funcs,
+				   DRM_MODE_CONNECTOR_DSI);
+	if (IS_ERR(ctx))
+		return PTR_ERR(ctx);
 
 	mipi_dsi_set_drvdata(dsi, ctx);
 	ctx->dsi = dsi;