ASoC: codecs: Kconfig: Show knob, and depend on MIPS || COMPILE_TEST

Show the knob to enable or disable the jz4740-codec driver, add a
proper description, and add a dependency on MIPS || COMPILE_TEST, as
this driver is only useful on MIPS.
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/Kconfig

@@ -579,8 +579,15 @@ config SND_SOC_CX20442
 	depends on TTY
 
 config SND_SOC_JZ4740_CODEC
+	depends on MIPS || COMPILE_TEST
 	select REGMAP_MMIO
-	tristate
+	tristate "Ingenic JZ4740 internal CODEC"
+	help
+	  Enable support for the internal CODEC found in the JZ4740 SoC
+	  from Ingenic.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called snd-soc-jz4740-codec.
 
 config SND_SOC_JZ4725B_CODEC
 	depends on MIPS || COMPILE_TEST