xfs: reject invalid flags combinations in XFS_IOC_ATTRLIST_BY_HANDLE

While the flags field in the ABI and the on-disk format allows for
multiple namespace flags, an attribute can only exist in a single
namespace at a time. Hence asking to list attributes that exist
in multiple namespaces simultaneously is a logically invalid
request and will return no results. Reject this case early with
-EINVAL.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Chandan Rajendra <chandanrlinux@gmail.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>