vp9 svc: Fix the stats output when sl = 1.
vp9 svc: Fix the stats output when sl = 1.

Actual frame size and bitrate is all 0 when using SVC sample encoder
with sl = 1 because the stats are set in parse_superframe_index which
will not caculate properly when sl = 1 since there is no superframe.

Use pkt->data.frame.sz instead when sl = 1.

Change-Id: I93f5e98a4c779e32b007e1564ba5396af9e34ad6

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