staging:iio:gyro:adis16060 cleanup and dead code removal

Removed stubs related to buffering and triggering. Put them back
when they are actually needed.
Fixed line length issues.
Made a number of functions static as no longer in header.

Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>