drivers: dac: mcp4728: set explicitly init priority

Since this DAC is connected via I2C bus the init priority
value must be higher than the default 50 so it can be initialized
later than the bus itself so add a dedicated init config
symbol for that.

Signed-off-by: Bartosz Bilas <b.bilas@grinn-global.com>

drivers/dac/Kconfig.mcp4728

@@ -7,3 +7,13 @@ config DAC_MCP4728
 	depends on I2C
 	help
 	  Enable driver for the Microchip MCP4728.
+
+if DAC_MCP4728
+
+config DAC_MCP4728_INIT_PRIORITY
+	int "Init priority"
+	default 80
+	help
+	  Microchip MCP4728 device driver initialization priority.
+
+endif # DAC_MCP4728

drivers/dac/dac_mcp4728.c

@@ -104,7 +104,7 @@ static const struct dac_driver_api mcp4728_driver_api = {
 	DEVICE_DT_INST_DEFINE(index, dac_mcp4728_init, NULL, NULL,		\
 				&mcp4728_config_##index,			\
 				POST_KERNEL,					\
-				CONFIG_DAC_INIT_PRIORITY,			\
+				CONFIG_DAC_MCP4728_INIT_PRIORITY,		\
 				&mcp4728_driver_api);
 
 DT_INST_FOREACH_STATUS_OKAY(INST_DT_MCP4728);