staging:iio:adis16350 replace unnecessary event line registration.

Whilst the adis163500 does indeed support events, currently the driver
does not.  The trigger code should never use that infrastructure.

Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Acked-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>