ASoC: AMD: Audio buffer related changes for Stoney

Stoney uses 16kb SRAM memory for playback and 16Kb
for capture.Modified Max buffer size to have the
correct mapping between System Memory and SRAM.

Added snd_pcm_hardware structures for playback
and capture for Stoney.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Vijendar Mukunda <Vijendar.Mukunda@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Mark Brown <broonie@kernel.org>