ASoC: spear: constify snd_soc_dai_ops structures

These snd_soc_dai_ops structures are only stored in the ops field of
a snd_soc_dai_driver structure, which is const.  Thus, the
snd_soc_dai_ops structures can be const too.

Done with the help of Coccinelle.

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Mark Brown <broonie@kernel.org>