filesetup: add engine's io_ops to prepopulate file with data

filesetup: add engine's io_ops to prepopulate file with data

In some cases (e.g. engine marked as diskless) files are not laid out.
If the first job is a read job, results are higher than expected
(because reading zero page). Each engine should deliver func to
prepopulate file with data to avoid this situation.

Signed-off-by: Łukasz Stolarczuk <lukasz.stolarczuk@intel.com>