ASoC: cleanups and improvements for jz4740-i2s

Merge series from Aidan MacDonald <aidanmacdonald.0x0@gmail.com>:

This series is a preparatory cleanup of the jz4740-i2s driver before
adding support for a new SoC. The two improvements are lifting
unnecessary restrictions on sample rates and formats -- the existing
ones appear to be derived from the limitations of the JZ4740's internal
codec and don't reflect the actual capabilities of the I2S controller.

I'm unable to test the series on any JZ47xx SoCs, but I have tested
on an X1000 (which is the SoC I'll be adding in a followup series).

sound/soc/jz4740/Kconfig

@@ -3,6 +3,7 @@ config SND_JZ4740_SOC_I2S
 	tristate "SoC Audio (I2S protocol) for Ingenic JZ4740 SoC"
 	depends on MIPS || COMPILE_TEST
 	depends on HAS_IOMEM
+	select REGMAP_MMIO
 	select SND_SOC_GENERIC_DMAENGINE_PCM
 	help
 	  Say Y if you want to use I2S protocol and I2S codec on Ingenic JZ4740