intel_th: msu: Get rid of the window size limit

Currently, the window size is limited to the maximum number of sg entries
in one table. This is because the code addresses individual blocks within
the window by their numeric index. In reality, though, the blocks most
often are iterated through sequentially. By rewriting the logic to use sg
pointers instead of block indices we loose the necessity to dereference
them directly and gain the ability to use multiple chained tables if
necessary.

Get rid of the limitation by replacing index-based block accesses with
sequential block accesses.
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20190705141425.19894-4-alexander.shishkin@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>