Do not reuse mv in base spatial layer if curr buf same as prev.
Do not reuse mv in base spatial layer if curr buf same as prev.

Bug: b/154890543
Change-Id: Iad5791912f781d225e610a61bc13f3dbaef81bb9

ShiftMediaProject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx