Build error against latest Linux tree

[cpackham]

Hi,

I just encountered the following error when building strace-5.7 (and earlier versions) against the latest linux tree

strace: In file included from ./static_assert.h:11,
strace:                  from xlat/uring_op_flags.h:4,
strace:                  from io_uring.c:14:
strace: io_uring.c:32:1: error: static assertion failed: "struct io_cqring_offsets.resv is missing, please update the decoder"
strace:  static_assert(0, "struct io_cqring_offsets.resv is missing"
strace:  ^~~~~~~~~~~~~

This is no doubt due to the linux commit 0d9b5b3af1 ("io_uring: add 'cq_flags' field for the CQ ring") which grabbed some of the reserved bytes and split the remaining bytes into resv1 and resv2.