sandbox: exynos: Move CONFIG_SOUND_MAX98095 to Kconfig

Move this over to Kconfig and tidy up.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/sound/Kconfig b/drivers/sound/Kconfig
index 1b97af0..cfc75cb 100644
--- a/drivers/sound/Kconfig
+++ b/drivers/sound/Kconfig
@@ -28,3 +28,11 @@
 	  using one of the available audio codec drivers. Enabling this
 	  option provides an implementation for sound_init() and
 	  sound_play().
+
+config SOUND_MAX98095
+	bool "Support Maxim max98095 audio codec"
+	depends on I2S_SAMSUNG
+	help
+	  Enable the max98095 audio codec. This is connected via I2S for
+	  audio data and I2C for codec control. At present it only works
+	  with the Samsung I2S driver.