drm/exynos: Use mode->clock instead of reverse calculating it from the vrefresh

htotal*vtotal*vrefresh ~= clock. So just use say "clock" when we mean it.

Cc: Inki Dae <inki.dae@samsung.com>
Cc: Joonyoung Shim <jy0922.shim@samsung.com>
Cc: Seung-Woo Kim <sw0312.kim@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos7_drm_decon.c

@@ -139,7 +139,7 @@ static void decon_ctx_remove(struct decon_context *ctx)
 static u32 decon_calc_clkdiv(struct decon_context *ctx,
 		const struct drm_display_mode *mode)
 {
-	unsigned long ideal_clk = mode->htotal * mode->vtotal * mode->vrefresh;
+	unsigned long ideal_clk = mode->clock;
 	u32 clkdiv;
 
 	/* Find the clock divider value that gets us closest to ideal_clk */