ASoC: meson: g12a-tohdmitx: Fix event generation for S/PDIF mux

When a control changes value the return value from _put() should be 1 so
we get events generated to userspace notifying applications of the change.
While the I2S mux gets this right the S/PDIF mux does not, fix the return
value.

Fixes: c8609f3870f7 ("ASoC: meson: add g12a tohdmitx control")
Signed-off-by: Mark Brown <broonie@kernel.org>