drm/rockchip: return a true clock rate to adjusted_mode

Since the mipi dsi driver need to use the clock of vop to make the
calculation of Blanking. But sometimes the clock driver can not set a
accurate clock_rate for vop, get it by clk_round_rate before mode_set,
so we can get the true value.
Signed-off-by: Chris Zhong <zyw@rock-chips.com>
Acked-by: Mark Yao <mark.yao@rock-chips.com>

drivers/gpu/drm/rockchip/rockchip_drm_vop.c

@@ -878,9 +878,14 @@ static bool vop_crtc_mode_fixup(struct drm_crtc *crtc,
 				const struct drm_display_mode *mode,
 				struct drm_display_mode *adjusted_mode)
 {
+	struct vop *vop = to_vop(crtc);
+
 	if (adjusted_mode->htotal == 0 || adjusted_mode->vtotal == 0)
 		return false;
 
+	adjusted_mode->clock =
+		clk_round_rate(vop->dclk, mode->clock * 1000) / 1000;
+
 	return true;
 }