drm/bridge: sii902x: fix missing reference to mclk clock

Add devm_clk_get call to retrieve reference to master clock.

Fixes: ff578163 ("drm/bridge: sii902x: Implement HDMI audio support")
Signed-off-by: Olivier Moysan <olivier.moysan@st.com>
Reviewed-by: Jyri Sarha <jsarha@ti.com>
Acked-by: Andrzej Hajda <a.hajda@samsung.com
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1563811560-29589-2-git-send-email-olivier.moysan@st.com

drivers/gpu/drm/bridge/sii902x.c

@@ -751,6 +751,7 @@ static int sii902x_audio_codec_init(struct sii902x *sii902x,
 		sii902x->audio.i2s_fifo_sequence[i] |= audio_fifo_id[i] |
 			i2s_lane_id[lanes[i]] |	SII902X_TPI_I2S_FIFO_ENABLE;
 
+	sii902x->audio.mclk = devm_clk_get(dev, "mclk");
 	if (IS_ERR(sii902x->audio.mclk)) {
 		dev_err(dev, "%s: No clock (audio mclk) found: %ld\n",
 			__func__, PTR_ERR(sii902x->audio.mclk));