ASoC: amd: acp: declare and add prefix to 'bt_uart_enable' symbol

Sparse reports the following warning:

sound/soc/amd/acp-pcm-dma.c:39:6: error: symbol 'bt_uart_enable' was
not declared. Should it be static?

It's not very good practice to export such symbols that can easily
conflict, add the acp_ prefix and add declaration in header file.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20210907184216.33067-1-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>
diff --git a/sound/soc/amd/acp-da7219-max98357a.c b/sound/soc/amd/acp-da7219-max98357a.c
index b3df98a..b2065f3 100644
--- a/sound/soc/amd/acp-da7219-max98357a.c
+++ b/sound/soc/amd/acp-da7219-max98357a.c
@@ -33,7 +33,7 @@ static struct clk *da7219_dai_wclk;
 static struct clk *da7219_dai_bclk;
 static struct clk *rt5682_dai_wclk;
 static struct clk *rt5682_dai_bclk;
-extern bool bt_uart_enable;
+
 void *acp_soc_is_rltk_max(struct device *dev);
 
 static int cz_da7219_init(struct snd_soc_pcm_runtime *rtd)
@@ -760,8 +760,8 @@ static int cz_probe(struct platform_device *pdev)
 				"devm_snd_soc_register_card(%s) failed\n",
 				card->name);
 	}
-	bt_uart_enable = !device_property_read_bool(&pdev->dev,
-						    "bt-pad-enable");
+	acp_bt_uart_enable = !device_property_read_bool(&pdev->dev,
+							"bt-pad-enable");
 	return 0;
 }