commit 4ce7ca89 upstream.

This patch uses iio_trigger_get to increment the reference
count of trigger device, to avoid incorrect assignment.
Can result in a null pointer dereference during removal if the
trigger has been changed before removal.

This patch refers to a similar situation encountered through the
following discussion:
http://www.spinics.net/lists/linux-iio/msg13669.htmlSigned-off-by: Darshana Padmadas <darshanapadmadas@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>