iio: dac: Fix duplicated entry in Kconfig

Signed-off-by: Paul Cercueil <paul.cercueil@analog.com>
iio: trigger: Remove unused / broken function

Signed-off-by: Paul Cercueil <paul.cercueil@analog.com>
iio: Fix build when buffer is disactivated

Signed-off-by: Paul Cercueil <paul.cercueil@analog.com>