ASoC: codecs: rk3308: depend on ARM64 || COMPILE_TEST

This codec is only known to exist in the RK3308 ARM64 SoC, so depend on it
except for compile test cases. Note that the driver won't probe without
CONFIG_OF, but ARM64 selects OF already so it is not needed.
Suggested-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Link: https://msgid.link/r/20240403-rk3308-audio-codec-fix-warning-v2-2-816bae4c1dc5@bootlin.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/Kconfig

@@ -1436,6 +1436,7 @@ config SND_SOC_PEB2466
 
 config SND_SOC_RK3308
 	tristate "Rockchip RK3308 audio CODEC"
+	depends on ARM64 || COMPILE_TEST
 	select REGMAP_MMIO
 	help
 	  This is a device driver for the audio codec embedded in the