[PATCH] aio: kill pointless ki_nbytes assignment in aio_setup_single_vector

io_submit_one assigns ki_left = ki_nbytes = iocb->aio_nbytes, then calls
down to aio_setup_iocb, then to aio_setup_single_vector.  In there,
ki_nbytes is reassigned to the same value it got two call stack above it.
There is no need to do so.

Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Acked-by: Zach Brown <zach.brown@oracle.com>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>