ASoC: AMD: Modified DMA pointer for capture

Give position on ACP->SYSMEM DMA channel for
the number of bytes that have been transferred on
the basis of current descriptor under service.

Signed-off-by: Vijendar Mukunda <Vijendar.Mukunda@amd.com>
Signed-off-by: Akshu Agrawal <akshu.agrawal@amd.com>
Signed-off-by: Mark Brown <broonie@kernel.org>