[PATCH resend] staging, lustre: fix a sparse error

[Al Viro]

On Fri, Oct 10, 2014 at 11:21:16AM +0800, WANG Chao wrote:

> I think __user annotation is for no dereferencing in kernel space. In
> this case, I think it's fine to override this error by __force. Because
> they're pointers with identical target types.

Umm...  The real question seems to be whether iovec is the right type in
the first place.  Does ->tx_iov ever contain a vector with _userland_
pointers?  If not, it ought to be struct kvec * instead.