staging: iio: dummy: add blank lines after declarations.

This fixes the following checkpatch.pl warning:
WARNING: Missing a blank line after declarations.

Signed-off-by: Catalina Mocanu <catalina.mocanu@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>