ASoC: amd: vangogh: Drop superfluous mmap callback

The mmap callback of vangogh driver just calls the default mmap
handler, and it's superfluous, as the PCM core would call it if not
set.  Let's drop the superfluous mmap callback.

Fixes: 361414dc

 ("ASoC: amd: add vangogh i2s dma driver pm ops")
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://lore.kernel.org/r/20210804075223.9823-1-tiwai@suse.de


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