io_uring/net: use proper value for msg_inq

io_uring/net: use proper value for msg_inq

struct msghdr->msg_inq is a signed type, yet we attempt to store what
is essentially an unsigned bitmask in there. We only really need to know
if the field was stored or not, but let's use the proper type to avoid
any misunderstandings on what is being attempted here.

Link: https://lore.kernel.org/io-uring/CAHk-=wjKb24aSe6fE4zDH-eh8hr-FB9BbukObUVSMGOrsBHCRQ@mail.gmail.com/
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>