xfs: do not need to check return value of xlog_kvmalloc()

In xfs_attri_log_nameval_alloc(), xlog_kvmalloc() is called
to alloc memory, which will always return
successfully, so we donot need to check return value.

Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Zhiqiang Liu <liuzhiqiang26@huawei.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>