io_uring: cleanup {g,s]etsockopt sqe reading

Add a local variable for the sqe pointer to avoid repetition.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/8dbac0f9acda2d3842534eeb7ce10d9276b021ae.1743357108.git.asml.silence@gmail.com


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