drm/sun4i: Move access control before setting the register as documented

Unlike what is currently being done, the ACCESS_CTRL bit documentation asks
that this bit should be set before modifying any register. The code in the
BSP also does this, so make sure we do this as well.
Reviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190118145133.21281-18-paul.kocialkowski@bootlin.com

drivers/gpu/drm/sun4i/sun4i_frontend.c

@@ -75,6 +75,10 @@ static void sun4i_frontend_scaler_init(struct sun4i_frontend *frontend)
 {
 	int i;
 
+	regmap_write_bits(frontend->regs, SUN4I_FRONTEND_FRM_CTRL_REG,
+			  SUN4I_FRONTEND_FRM_CTRL_COEF_ACCESS_CTRL,
+			  SUN4I_FRONTEND_FRM_CTRL_COEF_ACCESS_CTRL);
+
 	for (i = 0; i < 32; i++) {
 		regmap_write(frontend->regs, SUN4I_FRONTEND_CH0_HORZCOEF0_REG(i),
 			     sun4i_frontend_horz_coef[2 * i]);
@@ -90,9 +94,6 @@ static void sun4i_frontend_scaler_init(struct sun4i_frontend *frontend)
 			     sun4i_frontend_vert_coef[i]);
 	}
 
-	regmap_update_bits(frontend->regs, SUN4I_FRONTEND_FRM_CTRL_REG,
-			   SUN4I_FRONTEND_FRM_CTRL_COEF_ACCESS_CTRL,
-			   SUN4I_FRONTEND_FRM_CTRL_COEF_ACCESS_CTRL);
 }
 
 int sun4i_frontend_init(struct sun4i_frontend *frontend)