ASoC: tas2781: fixed compiling issue in m68k

fixed m68k compiling issue: mapping table can save code field; storing the
dev_idx as a member of block can reduce unnecessary  time and system
resource comsumption of dev_idx mapping every time the block data writing
to the dsp.

Signed-off-by: Shenghao Ding <shenghao-ding@ti.com>
Link: https://lore.kernel.org/r/20231002090434.1896-1-shenghao-ding@ti.com


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