ASoC: jz4740-i2s: add missed checks for clk_get()

jz4740_i2s_set_sysclk() does not check the return values of clk_get(),
while the file dereferences the pointers in clk_put().
Add the missed checks to fix it.

Fixes: 11bd3dd1 ("ASoC: Add JZ4740 ASoC support")
Signed-off-by: Chuhong Yuan <hslester96@gmail.com>
Link: https://lore.kernel.org/r/20201203144227.418194-1-hslester96@gmail.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/jz4740/jz4740-i2s.c

@@ -312,10 +312,14 @@ static int jz4740_i2s_set_sysclk(struct snd_soc_dai *dai, int clk_id,
 	switch (clk_id) {
 	case JZ4740_I2S_CLKSRC_EXT:
 		parent = clk_get(NULL, "ext");
+		if (IS_ERR(parent))
+			return PTR_ERR(parent);
 		clk_set_parent(i2s->clk_i2s, parent);
 		break;
 	case JZ4740_I2S_CLKSRC_PLL:
 		parent = clk_get(NULL, "pll half");
+		if (IS_ERR(parent))
+			return PTR_ERR(parent);
 		clk_set_parent(i2s->clk_i2s, parent);
 		ret = clk_set_rate(i2s->clk_i2s, freq);
 		break;