files: Fix conversion of pipe/fifo data

Need to write pde's at data payload start and
do that in cycle.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
todo: Get off the implemented entries

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
io: Add splice_data helper

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
files: Add conversion of ghost regular files

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>