cleanup ioengine_load() (for the next commit)

cleanup ioengine_load() (for the next commit)

This commit removes name argument from ioengine_load(), as both
ioengine name and path are self contained in td.
No functional changes.

This makes the next commit's diff more clear by separating non
functional noise.

Signed-off-by: Tomohiro Kusumi <tkusumi@tuxera.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>