drm/tegra: dc: Check for valid parent clock

Check that the desired parent clock is indeed a valid parent for the
display controller clock. This is purely cosmetic at this point since
the parent clocks are specified in DT and all the currently defined
parents are in fact valid parents of the display controller clock.
Signed-off-by: NThierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/dc.c

@@ -1177,6 +1177,9 @@ int tegra_dc_state_setup_clock(struct tegra_dc *dc,
 {
 	struct tegra_dc_state *state = to_dc_state(crtc_state);
 
+	if (!clk_has_parent(dc->clk, clk))
+		return -EINVAL;
+
 	state->clk = clk;
 	state->pclk = pclk;
 	state->div = div;