ASoC: sst_platform: fix memory leak

snd_pcm_hw_constraint_integer() could return -1, in this case, sst platform is
not opened successfully.  However the corresponding close callback isn't able
to be called later on to release these two allocated memories, thus resulting
in memory leak.

This patch moves the check for hardware contraints earlier, thus resolving this
issue.

Signed-off-by: Lu Guanqun <guanqun.lu@intel.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Acked-by: Liam Girdwood <lrg@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>