io_uring: add missing IORING_MAP_OFF_ZCRX_REGION in io_uring_mmap

Allow user to mmap the kernel allocated zerocopy-rx refill queue.

Signed-off-by: Bui Quang Minh <minhquangbui99@gmail.com>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: Li Zetao <lizetao1@huawei.com>
Link: https://lore.kernel.org/r/20250221085933.26034-1-minhquangbui99@gmail.com


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