staging: iio_simple_dummy: Fix indentation errors

Fixing indentation errors in
drivers/staging/iio/iio_simple_dummy_events.c.

Signed-off-by: Lars Svensson <lars1.svensson@sonymobile.com>
Acked-by: Daniel Baluta <daniel.baluta@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>