spi: qup: Setup DMA mode correctly

To operate in DMA mode, the buffer should be aligned and
the size of the transfer should be a multiple of block size
(for v1). And the no. of words being transferred should
be programmed in the count registers appropriately.

Signed-off-by: Andy Gross <andy.gross@linaro.org>
Signed-off-by: Varadarajan Narayanan <varada@codeaurora.org>
Signed-off-by: Mark Brown <broonie@kernel.org>