ASoC: fsl_mqs: Add MQS component driver

MQS (medium quality sound), is used to generate medium quality
audio via a standard digital output pin. It can be used to
connect stereo speakers or headphones simply via power amplifier
stages without an additional DAC chip. It only accepts 2-channel,
LSB-valid 16bit, MSB shift-out first, frame sync asserting with
the first bit of the frame, data shifted with the posedge of
bit clock, 44.1 kHz or 48 kHz signals from SAI1 in left justified
format; and it provides the SNR target as no more than 20dB for
the signals below 10 kHz. The signals above 10 kHz will have
worse THD+N values.

MQS provides only simple audio reproduction. No internal pop,
click or distortion artifact reduction methods are provided.

The MQS receives the audio data from the SAI1 Tx section.

Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Acked-by: Nicolin Chen <nicoleotsuka@gmail.com>
Link: https://lore.kernel.org/r/74dfc73a92d2df4213225abe7d2a3db82672fe0f.1568367274.git.shengjiu.wang@nxp.com


Signed-off-by: Mark Brown <broonie@kernel.org>