Fix constant correctness error in `getxattr`/`fgetxattr`
Fix constant correctness error in `getxattr`/`fgetxattr`

The system calls `getxattr` and `fgetxattr` return data in the pointer
passed as `value`, as is clearly layed out in the
[man page](https://man7.org/linux/man-pages/man2/getxattr.2.html)
for the actual syscalls.

Signed-off-by: Dominik Thalhammer <aeacd46bb4fd3f59504c7762d9af6bd04f20aa1f@thalhammer.it>

axboe/liburing,axboe/liburing,axboe/liburing