Drop redundant td_rw(td) tests

Drop redundant td_rw(td) tests

Since TD_DDIR_READ is 1, TD_DDIR_WRITE is 1<<1, and td_rw() requires
both TD_DDIR_READ/WRITE bits set, testing (td_read(td) || td_rw(td))
turns out to be

if td_read(td) is false, td_rw(td) is always false,
if td_read(td) is true, td_rw(td) won't be tested,
thus the result equals that of td_read(td).

It's the same for td_write(td) as well.

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