io_uring: pass ctx instead of req to io_init_req_drain()

io_init_req_drain() takes a struct io_kiocb *req argument but only uses
it to get struct io_ring_ctx *ctx. The caller already knows the ctx, so
pass it instead.

Drop "req" from the function name since it operates on the ctx rather
than a specific req.

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Link: https://lore.kernel.org/r/20250212164807.3681036-1-csander@purestorage.com


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