ASoC: meson: g12a-tohdmitx: Validate written enum values

When writing to an enum we need to verify that the value written is valid
for the enumeration, the helper function snd_soc_item_enum_to_val() doesn't
do it since it needs to return an unsigned (and in any case we'd need to
check the return value).

Fixes: c8609f38

 ("ASoC: meson: add g12a tohdmitx control")
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20240103-meson-enum-val-v1-2-424af7a8fb91@kernel.org


Signed-off-by: Mark Brown <broonie@kernel.org>