These functions fail with -EINVAL if the corresponding callbacks
are not implemented. Change them to return -ENOSYS as it is more
appropriate for unimplemented callbacks.
Signed-off-by: Dimitris Papastamos <dp@opensource.wolfsonmicro.com> Acked-by: Liam Girdwood <lrg@ti.com> Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>