iio: buffer: Kconfig: add title for IIO_TRIGGERED_BUFFER symbol

iio: buffer: Kconfig: add title for IIO_TRIGGERED_BUFFER symbol

For some embedded systems, a workflow involving external kernel modules
that implement IIO devices is more practical than working with in-tree
sources.

Kconfig symbols without any titles do not show up in menuconfig, and as
such are more difficult to configure granularly, as they need to be
selected by potentially unused/un-needed drivers.

This change adds a title to the IIO_TRIGGERED_BUFFER Kconfig symbol.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20200924111758.196367-4-alexandru.ardelean@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>