ASoC: sirf: Add audio usp interface driver

This patch adds ASoC support for SiRF SoCs USP interface.
Features include:
1. Only support slave mode.
2. Support I2S and DSP_A mode.
3. Support S16_LE, S24_LE and S24_3LE formats.
4. Support stereo and mono mode.
5. The biggest Support is 192Khz sample rate.

Signed-off-by: Rongjun Ying <rongjun.ying@csr.com>
Signed-off-by: Mark Brown <broonie@linaro.org>