iio: 104-quad-8: Fix active level mismatch for the preset enable option

The set_to_preset_on_index sysfs attribute provides a boolean
configuration option to enable a preset operation on the respective
channel's counter when Index occurs. However, the corresponding
configuration bit on the Input/Output Control register must be set low
to enable the preset operation.

This patch inverts the internal driver boolean logic exposed via the
set_to_preset_on_index attribute in order to correctly configure the
device which expects an active low bit.

Fixes: 28e5d3bb ("iio: 104-quad-8: Add IIO support for the ACCES 104-QUAD-8")
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>