[PATCH] ide: fix null request pointer for taskfile ioctl
When doing ioctl HDIO_DRIVE_TASKFILE, the ide_task_t's request pointer is
never set, but flagged_taskfile and do_rw_taskfile pass it as a parameter
to the prehandler. The kernel will oops taskfile pio-out commands because
of this (taskfile pio-in doesn't use a prehandler). This fix sets the
request pointer at the time the request is created to stop this oops.