ASoC: amd: Drop superfluous mmap callbacks

All ASoC AMD drivers just call the standard mmap handler, hence those
are superfluous.  Let's drop them.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://lore.kernel.org/r/20210728141843.17685-1-tiwai@suse.de


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