io_uring: delay sqarray static branch disablement

io_key_has_sqarray static branch can be easily switched on/off by the
user every time patching the kernel. That can be very disruptive as it
might require heavy synchronisation across all CPUs. Use deferred static
keys, which can rate-limit it by deferring, batching and potentially
effectively eliminating dec+inc pairs.

Fixes: 9b296c625ac1d ("io_uring: static_key for !IORING_SETUP_NO_SQARRAY")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>