[PATCH] dup fd error fix

Set errorp in dup_fd, it will be used in sys_unshare also.

Signed-off-by: Prasanna Meda <mlp@google.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>