LU-5971 llite: use vui prefix for struct vvp_io members

LU-5971 llite: use vui prefix for struct vvp_io members

Rename members of struct vvp_io to used to start with vui_ rather than
cui_.  Rename several instances of struct vvp_io * from cio to vio.

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: Iacdd982f82469c120bf801570b1bc152034d2a11
Reviewed-on: http://review.whamcloud.com/13363
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>