This callback structure has never been used and it is not clear why it
was added in the first place. Remove it to clear up the code a little.
Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20210211172106.16258-1-ckeepax@opensource.cirrus.comSigned-off-by: Mark Brown <broonie@kernel.org>