Staging: sst: fixups in SNDRV_SST_STREAM_DECODE

This is another patch about copying data to the kernel before using it.

SNDRV_SST_STREAM_DECODE is sort of tricky because we need to do a
copy_from_user() that gives us another two pointers and we have copy
those.  Those again give us some more pointers that we have to copy.

Besides those problems, the code had a stack overflow:
-	struct snd_sst_buff_entry ibuf_temp[param->ibufs->entries],
-		obuf_temp[param->obufs->entries];
param->ibufs->entries comes from the user.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>