ASoC: cs4271: Split SPI and I2C code into different modules

Currently the cs4271 driver depends on SND_SOC_I2C_AND_SPI.
So the driver cannot be built as built-in if CONFIG_I2C=m.
Split SPI and I2C code into different modules to avoid this issue.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Brian Austin <brian.austin@cirrus.com>
Signed-off-by: Mark Brown <broonie@kernel.org>