[PATCH] undo do_readv_writev() behavior change

Bugme bug 4326: http://bugme.osdl.org/show_bug.cgi?id=4326

 reports:

executing the systemcall readv with Bad argument
->len == -1) it gives out error EFAULT instead of EINVAL 


Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>