ASoC: amd: acp: Drop superfluous mmap callback

Remove mmap callback as ASoC AMD drivers just call
the standard mmap handler.

Signed-off-by: Venkata Prasad Potturu <venkataprasad.potturu@amd.com>
Reviewed-by: Vijendar Mukunda <Vijendar.Mukunda@amd.com>
Link: https://lore.kernel.org/r/20220721062043.3016985-2-venkataprasad.potturu@amd.com


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