vp9: Refactor set_low_temp_var_flag.
vp9: Refactor set_low_temp_var_flag.

No need to pass in force_split, since we should use sb_type in the
condition.

Change-Id: Ide27243ef46e017bbb98d676347fc566a6c828f7

ShiftMediaProject/libvpx,mwgoldsmith/vpx,mwgoldsmith/libvpx,ShiftMediaProject/libvpx,Topopiccione/libvpx,mwgoldsmith/libvpx,webmproject/libvpx,Topopiccione/libvpx,mwgoldsmith/libvpx,webmproject/libvpx,Topopiccione/libvpx,Topopiccione/libvpx,Topopiccione/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,mwgoldsmith/vpx,mwgoldsmith/vpx,ShiftMediaProject/libvpx,mwgoldsmith/vpx,mwgoldsmith/libvpx,mwgoldsmith/vpx,mwgoldsmith/libvpx,mwgoldsmith/vpx,mwgoldsmith/libvpx,webmproject/libvpx,Topopiccione/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx