ASoC: sirf-usp: Fixed a bug for playback and capture work at the same time

1. The startup function invoked when the playback and capture.
   If start playback when capturing, the registers are re-initinitialised.
   That cause the playback fail. So move the startup code into runtime resume.
2. Modified: If non RUNTIME_PM support, the probe need enable clock and
   initinitialise registers.
3. Refine code.

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