drm/exynos: use generic code for managing zpos plane property

This patch replaces zpos property handling custom code in Exynos DRM
driver with calls to generic DRM code.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>

Cc: Inki Dae <inki.dae@samsung.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Joonyoung Shim <jy0922.shim@samsung.com>
Cc: Seung-Woo Kim <sw0312.kim@samsung.com>
Cc: Andrzej Hajda <a.hajda@samsung.com>
Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
Cc: Gustavo Padovan <gustavo@padovan.org>
Cc: vincent.abriou@st.com
Cc: fabien.dessenne@st.com
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
diff --git a/drivers/gpu/drm/exynos/exynos_mixer.c b/drivers/gpu/drm/exynos/exynos_mixer.c
index 74a4269..e1d47f9 100644
--- a/drivers/gpu/drm/exynos/exynos_mixer.c
+++ b/drivers/gpu/drm/exynos/exynos_mixer.c
@@ -477,6 +477,7 @@
 	struct drm_display_mode *mode = &state->base.crtc->state->adjusted_mode;
 	struct mixer_resources *res = &ctx->mixer_res;
 	struct drm_framebuffer *fb = state->base.fb;
+	unsigned int priority = state->base.normalized_zpos + 1;
 	unsigned long flags;
 	dma_addr_t luma_addr[2], chroma_addr[2];
 	bool tiled_mode = false;
@@ -561,7 +562,7 @@
 
 	mixer_cfg_scan(ctx, mode->vdisplay);
 	mixer_cfg_rgb_fmt(ctx, mode->vdisplay);
-	mixer_cfg_layer(ctx, plane->index, state->zpos + 1, true);
+	mixer_cfg_layer(ctx, plane->index, priority, true);
 	mixer_cfg_vp_blend(ctx);
 	mixer_run(ctx);
 
@@ -586,6 +587,7 @@
 	struct drm_display_mode *mode = &state->base.crtc->state->adjusted_mode;
 	struct mixer_resources *res = &ctx->mixer_res;
 	struct drm_framebuffer *fb = state->base.fb;
+	unsigned int priority = state->base.normalized_zpos + 1;
 	unsigned long flags;
 	unsigned int win = plane->index;
 	unsigned int x_ratio = 0, y_ratio = 0;
@@ -677,7 +679,7 @@
 
 	mixer_cfg_scan(ctx, mode->vdisplay);
 	mixer_cfg_rgb_fmt(ctx, mode->vdisplay);
-	mixer_cfg_layer(ctx, win, state->zpos + 1, true);
+	mixer_cfg_layer(ctx, win, priority, true);
 	mixer_cfg_gfx_blend(ctx, win, is_alpha_format(fb->pixel_format));
 
 	/* layer update mandatory for mixer 16.0.33.0 */