io_uring: fortify io_pin_pages with a warning

We're a bit too frivolous with types of nr_pages arguments, converting
it to long and back to int, passing an unsigned int pointer as an int
pointer and so on. Shouldn't cause any problem but should be carefully
reviewed, but until then let's add a WARN_ON_ONCE check to be more
confident callers don't pass poorely checked arguents.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/d48e0c097cbd90fb47acaddb6c247596510d8cfc.1731689588.git.asml.silence@gmail.com


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