ASoC: AMD: disabling memory gating in stoney platform

For Stoney platform, Memory gating is disabled.i.e SRAM Banks
won't be turned off. By Default, SRAM Bank state set to ON.
Added condition checks to skip SRAM Bank state set logic for
Stoney platform.

Acked-by: Mark Brown <broonie@kernel.org>
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>