io_uring/zcrx: implement large rx buffer support

io_uring/zcrx: implement large rx buffer support

There are network cards that support receive buffers larger than 4K, and
that can be vastly beneficial for performance, and benchmarks for this
patch showed up to 30% CPU util improvement for 32K vs 4K buffers.

Allows zcrx users to specify the size in struct
io_uring_zcrx_ifq_reg::rx_buf_len. If set to zero, zcrx will use a
default value. zcrx will check and fail if the memory backing the area
can't be split into physically contiguous chunks of the required size.
It's more restrictive as it only needs dma addresses to be contig, but
that's beyond this series.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
[axboe: kill duplicate netdev_queues.h include]
Signed-off-by: Jens Axboe <axboe@kernel.dk>