ASoC: dmaengine: Use iov_iter for process callback, too

Along with the conversion to PCM copy ops, use the iov_iter for the
pointer to be passed to the dmaengine process callback, too.  It
avoids the direct reference of iter_iov_addr(), and it can potentially
help for the drivers to access memory properly (although both atmel
and stm drivers don't use the given buffer address at all for now).

Reviewed-by: Mark Brown <broonie@kernel.org>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Claudiu Beznea <claudiu.beznea@microchip.com>
Cc: Olivier Moysan <olivier.moysan@foss.st.com>
Cc: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
Link: https://lore.kernel.org/r/20230815190136.8987-23-tiwai@suse.de


Signed-off-by: Takashi Iwai <tiwai@suse.de>