Staging: sst: add some __user anotations

Staging: sst: add some __user anotations

This silences all the sparse warnings in intel_sst_app_interface.c.
It was just a matter of adding __user annotations, I didn't find any
real bugs here.  Quite a few of these were needed for stuff I added
earlier, sorry about that.

I removed a couple casts to (void *) that caused a warning like:
	drivers/staging/intel_sst/intel_sst_app_interface.c:606:27:
		warning: cast removes address space of expression
For example sst_drv_ctx->mailbox is already declared as
"void __iomem *mailbox" so casting it to void pointer isn't necessary
and it makes sparse complain because it removes the __user attribute.

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