ASoC: pxa: constify snd_soc_ops structures

Declare snd_soc_ops structures as const as they are only stored
in the ops field of a snd_soc_dai_link structure. This field is
of type const, so snd_soc_ops structures having this property
can be made const too.

The .o files did not compile for all the changed .c files.

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>