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/configs/arndale_defconfig b/configs/arndale_defconfig
index 3d5c870..f77209a 100644
--- a/configs/arndale_defconfig
+++ b/configs/arndale_defconfig
@@ -7,3 +7,4 @@
 CONFIG_CMD_SOUND=y
 CONFIG_I2S=y
 CONFIG_I2S_SAMSUNG=y
+CONFIG_SOUND_MAX98095=y