ASoC: Staticise sst_pcm_new and sst_soc_platform_drv

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by Vinod Koul <vinod.koul@linux.intel.com>
Acked-by: Lu Guanqun <guanqun.lu@intel.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>