io_uring/rw: recycle buffers manually for non-mshot reads

io_uring/rw: recycle buffers manually for non-mshot reads

The mshot side of reads already does this, but the regular read path
does not. This leads to needing recycling checks sprinkled in various
spots in the "go async" path, like arming poll. In preparation for
getting rid of those, ensure that read recycles appropriately.

Signed-off-by: Jens Axboe <axboe@kernel.dk>