ASoC: amd: Report accurate hw_ptr during dma

Using hw register to read transmitted byte count and report
accordingly the hw pointer.

TEST=
modprobe snd-soc-acp-pcm.ko
modprobe snd-soc-acp-rt5645.ko
aplay <file>

Signed-off-by: Vijendar Mukunda <Vijendar.Mukunda@amd.com>
Signed-off-by: Akshu Agrawal <Akshu.Agrawal@amd.com>
Tested-by: Akshu Agrawal <akshu.agrawal@amd.com>
Reviewed-by: Jason Clinton <jclinton@chromium.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Mark Brown <broonie@kernel.org>