Revert "io_uring: don't use int for ABI"

This reverts commit 17a66aef which is
commit cf73d997 upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: If9e4b9b5a6b597855d96f209711c3c9c22bc09a6
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>