erofs-utils: mkfs: skip xattrs where getxattr() returns ENODATA

For example, unprivileged users may not have access to the `trusted.*`
namespace.

It also dumps unidentified xattrs with index 0, which the kernel/FUSE
implementations will ignore.

Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20250621132840.3036887-2-hsiangkao@linux.alibaba.com
1 file changed