drm/stm: ltdc: switch to regmap

Replace the legacy register access by regmap API.
Signed-off-by: Yannick Fertre <yannick.fertre@foss.st.com>
Acked-by: Philippe Cornu <philippe.cornu@foss.st.com>
Reviewed-by: Philippe Cornu <philippe.cornu@foss.st.com>
Reviewed-by: Raphael Gallais-Pou <raphael.gallais-pou@foss.st.com>
Tested-by: Raphael Gallais-Pou <raphael.gallais-pou@foss.st.com>
Signed-off-by: Philippe Cornu <philippe.cornu@foss.st.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211215214738.19946-1-yannick.fertre@foss.st.com

drivers/gpu/drm/stm/ltdc.h

@@ -32,6 +32,7 @@ struct fps_info {
 
 struct ltdc_device {
 	void __iomem *regs;
+	struct regmap *regmap;
 	struct clk *pixel_clk;	/* lcd pixel clock */
 	struct mutex err_lock;	/* protecting error_status */
 	struct ltdc_caps caps;