ASoC: rt5514: add rt5514 SPI driver

The device has multiple control interfaces, I2C and SPI. The I2C interface
mainly controls the register settings of codec. The SPI interface is in
order to provide the high speed transmission of data. For example, high
bandwidth memory read/write of DSP. The patch adds the rt5514 SPI driver
for loading the firmware of DSP and retrieving the voice data from DSP
after the system is waked up by specific voice.

Signed-off-by: Oder Chiou <oder_chiou@realtek.com>
Signed-off-by: Mark Brown <broonie@kernel.org>