d_alloc_name return NULL in case error, but we expect errno in
devpts_pty_new.

Addresses http://bugzilla.openvz.org/show_bug.cgi?id=1758Signed-off-by: NAndrey Vagin <avagin@openvz.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>