iio: trigger: allow devices to suspend/resume theirs associated trigger

iio: trigger: allow devices to suspend/resume theirs associated trigger

When a machine enters a sleep state while a trigger is associated to
an iio device that trigger is not resumed after exiting the sleep state:
provide iio device drivers a way to suspend and resume
the associated trigger to solve the aforementioned bug.

Each iio driver supporting external triggers is expected to call
iio_device_suspend_triggering before suspending,
and iio_device_resume_triggering upon resuming.

Signed-off-by: Denis Benato <benato.denis96@gmail.com>
Link: https://patch.msgid.link/20240807185619.7261-2-benato.denis96@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>