ASoC: rt*: Constify static struct sdw_slave_ops

ASoC: rt*: Constify static struct sdw_slave_ops

The only usage of these is to assign their address to the ops field in
the sdw_driver struct, which is a pointer to const. Make them const to
allow the compiler to put them in read-only memory.

Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Link: https://lore.kernel.org/r/20210224211918.39109-2-rikard.falkeborn@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>