drm/atmel-hlcdc: revert shift by 8

Revert shift by 8 of state->base.alpha. This introduced a
regression on planes.

Fixes: 7f73c10b ("drm/atmel-hclcdc: Convert to the new generic alpha property")
Cc: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1556195748-11106-7-git-send-email-claudiu.beznea@microchip.com

drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_plane.c

@@ -382,7 +382,7 @@ atmel_hlcdc_plane_update_general_settings(struct atmel_hlcdc_plane *plane,
 			cfg |= ATMEL_HLCDC_LAYER_LAEN;
 		else
 			cfg |= ATMEL_HLCDC_LAYER_GAEN |
-			       ATMEL_HLCDC_LAYER_GA(state->base.alpha >> 8);
+			       ATMEL_HLCDC_LAYER_GA(state->base.alpha);
 	}
 
 	if (state->disc_h && state->disc_w)